8MM retainers/locks on 5/16 valves: OK or not OK?

Lunati swears that the Lunati 75740 retainers and the Lunati 8Mm locks will work & others said if they fall down on the stem under their own weight then they will not (& they did). I got some different Lunati locks 13151 (for 5/16 valves) but the lash cap recess perimeter is .017" above the valve tip. Agreed I am gonna try (maybe) grinding the 5/16 lash caps I already have as CC/Manley & Lunati after many ph calls have nothing that they can find that will solve this. The CC 5/16 lash caps I ordered yesterday I found out today will not work cuz the .080 (posted) dimention is the inside dimention not the total height. This will be a circle track eng buzzing to maybe 6300 tops. If you guys think I can get by with some 7 deg retainers/locks in this app (142 lbs closed/308 lbs open) maybe I will have better luck. There is .125" from the top of the (bead) lock groove to the top of the valve. I am certainly open to advice/suggestions/guidance! I am hitting the wall here! RR