@abalakov @roflsocks @markbrouns Appreciate the responses. Many of the things you guys said are along the lines of my thinking (particularly fatigue resistance/TTE, etc).
I hope my genetic limit is still far away in terms of VO2max! 
I’ve been following these scientific”ish” posts with some interest but I’m still left wondering what the purpose is of such specific physiological testing and training protocol for athletes that aren’t already at a very high level of their physical potential? The whole idea of marginal gains has been turned into an excercise in conspicuous consumption.
If the OP is at 3.92w/kg as stated, I’d imagine that more volume in a well designed standard periodized plan of any sort would illicit improvement. There’s still regular everyday gains to be had but regardless of training moving forward he can now attribute improvement to a lab test and sports science that very well could have nothing to do with his new 4.1w/kg FTP…
Just my opinion of course, but I’m very interested in other’s thoughts and experience with long term training and verifiable improvements, however marginal;)
I think the OP is actually a great example of why such specific physiological testing is potentially really beneficial to a non-elite athlete. With such a low VLaMax and plenty of room for improvement with his VO2Max he now knows exactly what type of training to target in order to get maximum improvement (assuming he gets his plan correct I’d imagine the gains could be way more than “marginal”). No point wasting a ton of time doing sweet spot if improving VO2Max is going to give way bigger gains. I guess time will tell; we’ll be able to see if all this theory is correct in 12 months time 
I guess I just wonder if we really needed lab data to figure out if OP needed VO2 work.
To me, it was fairly obvious from the statement “I’ve mostly done Tri plans for the past two years”
This.
@stevemz Exactly. I’d also think a basic power profile would be plenty of data to build an effective plan for your run of the mill amateur athlete to see improvement.
Some of the tri plans have got a load of VO2Max work in there.
Take Olympic Triathlon Build:
https://www.trainerroad.com/cycling/plans/225-olympic-triathlon-build-low-volume
Like @oggie41 says there’s plenty of VO2 Max stuff in the Triathlon plans of all distances, more so than some of the pure cycling plans
I’ve been a fan of field tests for years, and am interested in professional testing. However the $300-450 cost in INSCYD FAQ stopped me cold.
OT HV Base: 300 TSS and 1 VO2 workout total
OT HV Build: 330 TSS and 1 VO2 workout per week
OT HV Specialty: 342 TSS and 1 VO2 workout per week
This is not a significant amount of VO2 work and is a pretty minimal amount of TSS (which makes sense since they are Tri plans).
Don’t get me wrong, I love reading about the data, but it just seems like a very expensive and invasive protocol.
@tshortt totally get it, takes time to educate yourself. Going INSCYD or using a local coach that does testing is a great way to establish a baseline and plan without going the DIY route.
@tshortt Maybe I’m just a curmudgeon… I just bought a new (used) 2016 aluminum frame to throw my 2009 SRAM Red 10spd group on and I’m so excited I’m beside myself;)
I’m the wrong guy to ask about marginal gains. A road racer that doesn’t even own an aero helmet and races 40mm deep tubulars… (And just got a real power meter in December)
But I ride. Lots.
@bbarrera Now, having said that, I get what you’re saying too. What I didn’t say before was another reason I did it was that I just thought it was fun.
I’m interested and think it would be fun too, but not at the price range listed in the FAQ.
Keep mind though, for you guys the gains might be marginal. For me, they are not. I have plenty of low(ish) hanging fruit type improvements. Without the INSCYD data (or a coach telling me), I would’ve never taken on a VO2max focus this time of year.
I also would not have known that I chronically under-fuel. I hate admitting that. But the data is there.
Please don’t misunderstand me, my point is that I think 99.9% of us on this forum aren’t to the point of needing to stress marginal gains. I’m at around 4.7w/kg and I don’t think I’m anywhere near there yet.
I feel that the issue becomes losing sight of long term improvement for instant gratification. Sure you can do a VO2 block and see and feel the difference, but you can also ride more Z2/SS and get the same boost and a big endurance improvement. But it takes more time and work. Cycling is an aerobic sport after all.
I get that people want to maximize performance and minimize training volume. I’m just not one to look for magic bullets. If I couldn’t train this much I wouldn’t expect to perform at the same level and would be fine with that. Realistic expectations and all that good stuff.
Comparing TSS between cycling and triathlon plans is pointless as you say because there’s a lot of other work involved in the triathlon plans with the other training. Cycling and triathlon are different sports.
I could quote this for example as a cycling progression with even less VO2 work 
SSB HV Base 0 VO2 workout total
Sustained Power HV Build 1 VO2 Max workout per week
Century Speciality 3 VO2 sessions total
The key for any of us is to pick the plan that best meets our needs based on our own physiology and racing/outcome goals. Fortunately there are plenty of choices within the TR framework to do that.
We can all make educated guesses as to what type of progressions we as athletes need and sometimes testing like INSCYD protocols can help to confirm what we probably already have a reasonable idea about.