Most power meters have a stated accuracy of about 1%, so from my perspective 1.5% is just about in the noise. If your FTP was around 300 watts, thats a difference of 4.5 watts. I track in 5w increments, but I don’t think 4-5w super noticeable and could easily be explained by a variety of factors on test day. I would use whichever number you want, but wouldn’t be concerned about it.
Good job on the 14% bump. That is a nice increase and probably made SSBII feel much more difficult than SSBI. Your SS intervals in SSBII were higher than your threshold intervals from SSBI! That takes some adjustment to recalibrate your perceived exertion.
An option, if you don’t want to commit to a full build, would be to just do the first half (4 weeks.). You’d get a taste and be better mentally prepared for next time but wouldn’t have to deal with the full deal.