shimming hydraulic roller lifters solid

You certainly can adjust a [ hyd ] lifter off the bottom. They are designed so that the piston assy can be anywhere from bottomed out...to touching the circlip. The preload from the small internal spring is nothing....compared to the other spring it is competing with: the valve spring. You can compress the lifter spring with pliers. Even with a relatively 'soft' valve spring of 100 lbs on the seat with 1.5 rockers, that is 150 lb [ that is with the valve on the seat & it goes up from there....], the lifter spring is a non -player.

ot sure how old DV is, 80-ish I think.