Solid roller lifters...

BAM lifters ....

This is the opposite side of the lifter in relation to the oil gallery.
The small pushrod oil feed hole is only on this side.
Oil from the gallery is fed from the other side thru the big hole, then it’s an edge orifice scenario to get oil into the small hole.
My customer isn’t going to use the pushrod oiling, so the small hole being exposed at full lift isn’t a concern in that aspect.
You can see that if the small hole is being exposed, then the top of the big hole is getting close to the top of the lifter bore.
So, the test is to see if there is any significant leakage around the top of the lifter bores when the lifters are near full lift.