I have only a little experience with O. boehmi and I haven't been lucky finding much info about opistophthalmus spp. There is something here http://www.ntnu.no/ub/scorpion-files/o_glabrifrons.php I keep my O. boehmi mostly like written and they seems all doing fine.
This is how I keep my O. boehmi...
1. about 25 degrees daytime,a little lower at night.
2. 10cm or more
3. mostly dry / 60-70 %
4. O. boehmi is about 5cm bodysize / 9cm total
You must be aware that they would spend most of there time in there hide.My male is what I see most,my females isn't to keen to come by and say hello ;-) You could call them petholes,if you know what I mean...