I'm following - I would never use the W-hold types of sleeves with the flat nubs - the X High-Tech nub just came with that type of sleeve as well as this one pictured.
I used the Blue softer prometheus nub and it actually just squished around (used a VFC clear hop up chamber to watch exactly what was happening - smart right?
) which misformed the nub
I still have the black harder prometheus flat nub that I might give a shot with your idea of shaving down the mound and adding rubber from another hop up - unless ofcourse it actually doesn't need that extra bit of material.
Side note: Apologies to the OP if we're totally derailing your entire thread in reference to the R-Hop mods. I honesty just can't get enough of ideal hopup/range mod talk with different options!