This is my first time doing trainer road, but I started with SSBLV in the middle of the winter, I would add some volume here and there because I am normally used to a higher training volume than the LV plan could provide. I just switched to General Build Mid. vol. and have been loving the volume, I stick to the plan pretty much 100% except I have the first group ride of the season in stead of my Sunday work out next week. I noticed that I much more enjoyed sticking to the mid volume plan than adding to the low volume plan, the plans are so well structured that when you follow them they just work.
As of now I have the Low volume crit plan on my calendar for after I finish build but now I am second guessing splitting my workouts between indoors and out.
In the end if your over all training volume will only come from TR then I would be cautions of changing volume plans but finding what works for you is the real key.