Tranny won't mount

even with the plastic guide there is enough wiggle that if you do not hold it centred while you evenly and uniformly tighten the pressure plate bolts, the disc can be off centre enough so the input shaft hangs up in the pilot bushing. I have had to have someone depress the pedal to disengage the clutch disc so that it can move to where it wants and needs to be for full engagement of the transmission input.