The continuity ring can't be loose. The light will not work.
As for making it a dual level light, it may be easier to install a multilevel driver than to replace the switch with a 2 level switch.
The reason your MofoClicky doesn't screw down all the way is because the heatsink and reflector assembly is TOO tall. Unfortunately there is a limited amount of space in the head any mod which is taller than the original driver emitter optic assembly. Basically it is OUT OF SPEC. The depth of the driver is critical. too shallow (your condition) and only twisty's work properly. too deep and the battery can't make contact with the driver board.
It is tricky to get a front glass/reflector/emitter/driver/heatsink all to fit.
I have a couple of modded Arcs which do in fact have all of the components required that fit into the space and also allow the MofoClicky to fit properly. It really takes a top flight modder to make these mods and have the light operate perfectly with twists and clickies.
I am going to play with installing a 2 level switch into a mofoClicky.
If I manage to do it and have it work reliably I will post images which show how to do it.
I wouldn't hold my breath. I have never been a huge fan of 2 level switches of any kind. I have never found that they operate 100% for me. I prefer either a single ON OFF clickie or to run a driver which makes use of the momentary on ability of a switch like the (McClicky) mofoClicky to act as a logic for a driver. Using a driver to set the levels is much more flexible, including the ability to set several levels and a strobe and or SOS feature.
The Piglet has these features and fits into an ARC nicely with the correct heat sink.
BTW guys I still have some MOFOClicky's So feel free to order anytime.
If you are an ARC owner and are on the fence I will send you a MOFOClicky to try. If you like it (I am Betting that you will) you send me the cash. If you don't you send me the AS NEW MOfoClicky back.
How is that for a deal? Sorry open to USA customers only (shipping these around the world for trials is too expensive). If you want to take me up on this offer PM me and we will arrange it.
I say there is nothing like a free test drive.
Yaesumofo
The McE2S switch assembly would replace the Mclisky switch. The McE2S delrin ring would retain the rubber boot and the continuity ring (or a similar ring)would have to be re-installed loosely after the McE2S to provide operating room for the McE2S. But the McE2S does require slightly bigger clearance at the battery end as noted previously.