I got a M340 PRO. Was entirely disappointed and sold it immediately. It's just a regular scout light with a proprietary mount that doesn't do anything that you can't do better with a hard-mounted MLOK solution.
If you're using a M1913, unless you have the mount in the stowed position, it stick WAY out. So at that point, just get a regular scout.
Regardless of Mlok or M1913, the lockup isn't very secure. In order to tighten the rotating mount, you have to remove the head. If you're trying to clear a PEQ15, it helps to have the head on the light so you know what your clearance is before tightening the mount down.
Also, the wimpy slotted head screw that clamps the mount to the rail is worse than the one that was on the RM45. Overall, wasn't a fan. I'd rather just have a regular scout. YMMV