Think I covered most of those question in Seiler his results thread. Ill try to link here.
Re: Doing now…
One challenge is doing the long 3 - 4.5 hr rides when you can’t get outside or there is bad weather or short day light hours.
Finally I think it takes longer to gain performance than Threshold training (I see SST and Threshold training as a quick fix) but its a ‘deeper’ fitness, especially if you can exceed 10hr per week. My performance seemed to stay the same for the first 6 - 8 weeks but I felt better in everyday life. Think we are talking 3 months plus for really solid gains.