XR-E in a plastic enclosure?

I've been asked to boost the output on an all plastic Nerf scope.

So the question is what sort of current can I put through an XR-E with out it getting to hot?

It would be easy enough to add quite a lot of metal to act as a heat sink inside the case, but is that a waste of time if it's entierly enclosed?

It looks like 700ma is the maximum recomended current for the XR-E, does 350ma sound sensible?

How long at a time will it be switched on for? If it is seconds at a time and not too many times an hour then you'd be able to get away with 1.4A.

If it is going to be on for tens of minutes at a time I'd reckon 700-800mA would be wiser. A large chunk of the densest metal with the highest specific heat capacity you can get for a sane price (Last time I looked, osmium cost more than platinum) will help but think in terms of duty cycle.