Kray on my MVVS 1,5 the compression screw does not have enough threads left on top to do this. If you get a metric allen screw of sufficent length wull work fine a piece of brass flat stock 1/8 " thick would be fine for the locking lever the reason I double the thickness on mine at the end was because I only had 1/16th of course make sure you do not run the contra down to far that it will strike the piston this can be checked by just turning the engine over slowly by hand and when you get interferance back if off to clear you can adjust the length by simply using a small washer under the bar and cutting the screw so it not too long alo you can finish the screw
end to remove any sharp edges on its bottom maybe round it a little with a dremel. So far my MVVS 1.5 has not had this problem\
my MVVS 61 has a davis head so no issue there my orginal 61 diesel head Francis Pierson has If he sees any issues sure he will do the same or similar Not really sure about this but I think Davis suggestd the "hole idea" for the stock heads, not an issue in his martin