The weak side hand placement will work without a Unique thumb relaxation. Thumb relaxation from Ronni works on MCK If you prefer. Shoulder strap attaches on both. No pistol brace extension desired. MCK uses pistol's slide release so no mal-capabilities like Ronni. The only thing the Ronni has the MCK https://franciscoxjvgl.p2blogs.com/25702759/considerations-to-know-about-recover-tactical-20-20