Although the older version hybrid, I've been water testing a modified LS too.
This SLS has been modified with the idea borrowed from the other thread where sealant is used around the optic, and the circuit potted with epoxy.
After sealing, the optics do not leak at all, and the Kroll tailswitch proves to be water resistant also if screwed on tightly.
However the one week link is that the o-ring seems to be either too small or the lip of the head is too wide, after lubing it can be turned very easily and perhaps too easily. A second o-ring of the same size (which I robbed another battery pack for) can be fitted just above the first o-ring. This might provide for a better seal until I can find another thicker o-ring.
Peter, if you don't mind me asking, what are the diamensions for the o-rings used? And have you considered using two o-rings since no changes need to be made to the pack?
-YC