Wondering how to measure dove-tails on a rifle. 3/8" or 11mm. Is it from the dove tail edge or the dove tails groove?!?!?!? Needing a compact rail adaptor to a weaver system, but can't find one. 100mm length adj. one pieceis too long for my rifle!!! Need some advice. Optic planet search bar is confusing at results, but two piece ring would be fine too. Anyone got any ideas?!?!?!? Thanks, tjk