I had a couple LA 509 cams I checked, and they actually have ramps not far from mech. cams. I think the ramps were something like .008-.010 camlift. This means you could in principle use these cams with solid lifters adjusting lash to the same, multiplied with the rocker ratio. I would adjust it hot, to be sure you are not way off. I ended up not using these cams for the intended use, as they would kill low end power. I have saved them for budget builds intending to use with solid lifters. I have no idea why they are made this way. I have checked other hydraulic cams, and I found more cams with small ramps in them. Maybe they need to cushion the lifters in the start of the lift?
That being said I do know a very knowleable and capable sport car crew cheif that does that exact same thing on a GM 305 C.I. "spec" motor class where they limit the lift at the retainers, I think 
. He had a cam ground with hydraulic lifter lobes that would meet or check legal in the tech. check or tear down, he put some of the high dollar Schubeck solid lifters in it and stepped the valve spring pressures way up and set the lash at .002 hot. The tech guys always use the old GM .030 hot lash setting for all of their inspection procedures 
.028 more lift and more effective duration 
