Nice score!
I guess the uvb decision could be affected by how often you want to change the bulb (the 6 month thing) - with a 2' long uvb florescent style bulb, that'll run about $50 annually for just the bulbs (may or may not be a decision factor). When I had a high maitenance planted aquarium I came to resent replacing the bulbs, oddly.
With uvb lights you you have different percentages of uvb, perhaps a lower percent (like a turtle type vrs. a desert lizard type) might reduce the worry over their eyes? I don't really know, just something you could look into.
The only lit I have read regarding crustacean eye damage is mostly relevant to aquatic types & so deals more with eye-types that aren't like our crabs'.
You get about a foots worth of uvb penetration directly under the unshielded bulb for the whole length of the tat, and may want to offer areas where the uvb is shielded, though I suppose there are always a lot of hides available.
There's also the consideration that based on what scanty research into the subject points to, crab community investigators have often concluded there's no specific reason to believe uvb is necessary/beneficial to our adult crabs (at least as far as vitamine D production is concerned - there are decided effects of both uva & b on decapod larva, but I havent personally sifted though any of that literature, so can't speak to it... I was looking for a paper that seemed primarily to be the source of the conclusion but I filed it sloppily, and havent read it - sorry) ...
... Though (somewhat anecdotally), the majority of strawberry keepers ive read the opinion of seem to find it makes a difference with this species (and straws are comparatively short lived in captivity, so I'd imagine people would really have a chance to notice the difference with them, whereas with the hardier species its harder to note that correlation... I'd expect.)
I personally like just a natural daylight colour spectrum bulb for my crabs. I think that should facilitate normal vision for them. Uvb isn't passing through the window in a substantial way anyhow.
Just thoughts.
