Sean/ Scott
Nowadays the diochroics come with a flat glass front. I presume this is for safety reasons in normal usage. If you use them underwater without modification, water seeps in leaving a pool of water inside, which causes a 'wobbly' reflection in use, and then goes misty & diffuse with trapped water after. The old ones without a front glass were fine, and maintained the published beam pattern (I normally aim for 10 degree beam).
So you have two options - remove the glass entirely or drill holes in it to let water in then out againafter the dive.
Drilling two holes (top and bottom) about 3mm/ 1/8th inch will do the trick. However, tapping the front glass witha sharp point will break it, then pick out the bits of glass stuck/ glued to the edge. It may take you one or two tries to get the knack, but IMHO getting rid of the glass is the best way.
E-mail me direct (scoff_cavedivinggroup@hotmail.com) if you have further questions.
Cheers
Scoff