If they are the same as a hydraulic, then what's to stop it from trying to pump up? Is removing the disc valve all it takes? That's what I've been getting at. That's why I don't think the idea to shim them solid is a good one. If the lifter continues to try to pump up, then surely sooner or later it will pop the wire clip out and come apart. The pump up part of the hydraulic lifter must be defeated.
Well on the EDM SFT lifter the snap ring holds the cup in place and the EDM hole is constantly bleeding oil so no pump up happening there. If your using the AMC style pushrod oiling you also have another oil bleed.