You need to measure the pushrod length at ZERO lash (plunger in the lifter at the top) and be fairly accurate, and then add your preload. .050 preload is right in the middle of the range and they’ll take as much as .090. If you adjusted the pushrod, collapsing the lifter, then added preload you’ll hold the valves open.
I thought about that. It looks like all the plungers are right up against the retaining clip at the top of the lifter. Hope that means they're at the top of their travel. I don't think I put enough pressure on them to push them down any.