I like to set my reverse up between .050 and .070. Not sure what the fluid aould cbange, I have not tested fluid to see the effects of different weights. Not thinking the clearance was and issue in the brake holding as you indicated the clutches looked new, and with having changed the Valve body Im guessing your old solenoid was not holding. Your et loss could be many things, the fluid, the new VB could have higher pressure meaning more converter pressure effectively toghtening it up, the VB may not shift as clean or it could be a combo of all.