Most reverse manual VB instructions state to discard the spring. I typically add a 1/2" diameter x 3" steel rod between the bottom of the accumulator bore and the piston. Double check that the valvebody sits down on the case before tightening the bolts. If the piston holds the VB from sitting flush on the case, you would need to shorten the blocker rod a small amount. Discarding the spring and blocking the piston down firms the 1-2 shift.