I don't know of any sites offering design, but what I have noticed is the vast difference in size between tabernacles irrespective of the size of yacht it's fitted to.
We are a 26ft. ketch with a main mast just 24ft. in height but the tabernacle is approaching 30inches in height, made of at least 10mm galavanised steel and secured to the cabin roof with eight 16mm bolts. Next door is a 34ft ketch and the tabernacle on that looks as though its made of pressed" tin" and is under 12inches in height.