Training for Shorter Time Trials

Hi all, just looking for some advice on training for shorter TTs.

With the current lull in races I thought it would be a good point to re-evaluate my training. I wintered well with completing a good base and sustained power build phase. In my first few races of the season (1 win, a 3rd and a 9th) I performed well thanks to the structure TR has given me. However I have noticed that during the shorter races I struggled to hold anything above my FTP for any length of time. For instance I had a normalised power on a hilly 26M TT of 338W (FTP of 340), which I was happy with. However on the shorter races I struggle to hold anything above my FTP for any length of time ending up with a similar normalised and average power of around my FTP. I think my current base and build phases have made me more economical at performing around my FTP, which I suppose is the main end goal.

I understand that going above your FTP is tough in any regards, however a lot of my later season races will hopefully be 10 mile TT’s (in the UK most time trials are 10s). So I’ll be aiming for a time of around 20/21 mins depending on the course. With that in mind I was planning to do the 40k TT plan (I do have a couple 40k TTs planned), building into the main bulk of the season, however would I benefit from a bit more work above VO2+? Reading from a few different sources including Matt Botrills blog (former UK 10M TT champ), that he even incorporated 1 min max efforts into his training for 10M TTs.

Any advice much appreciated,