Typical P60 drop in measures 21.66-21.8mm by my examples I have on hand, the Solar Force L2T host diameter is 22.6mm, so quite an air gap, it may touch the host at the brass base or hanging up on the reflector itself, this will vary naturally from manufacture to manufacture of the P60 drop in and host.

Of course the more contact the better….and there will always be thermal issues with over driving LED’s, the P60 by design just needs much more help thermally.