These are good questions...Yes, I agree it is time to decide to live with it, sell the truck, or pour more money in at a new shop. 2 questions. If the corvette servo or the band clearance there is giving the harsh shift, would it not also shift harsh in 4th? I thought the band also applies in 4th. I was wondering if that would help us decide. My other gears shift nice.
Does it make sense to take my accumulator and just flip the piston to to a legs up piston and put the single spring on top?
1. The fourth gear apply circuit has a lot more accumulation and, by design, is much softer shifting than 2nd gear. As from the factory, the 3-4 upshift feed hole in the spacer plate is markedly smaller as well. So excessive band clearance won't have the same effect on the 3-4 upshift as it does on the 1-2. Again, this assumes everything is held 'equal' (i.e. no mods to the transmission in any way, baselining it from the factory)
2. You can try to flip the piston to see what sort of effect it has...Transgo has you do something similar to the 700R4 in all of their 700R4 shift kits...They use an in-board spring, have you put the piston on top of that spring, legs facing the spacer plate, then you install a larger spring between the up-turned piston and spacer plate.