Lots of good information in the CBG Bass group:
The one I made had a 27inch scale.
I don't have any experience but I have had one bouncing around in my head for a while (Oh, painful). One thing that seems worth working out is not only about the scale length but also the string length (not the same). If you make a short scale bass (say about 30" or whatever) and use a hard tail bridge you will need short scale strings. You may already know that you can't just cut normal ones short as they are so thick that they have to be thinner at the end where they wrap round the machine head. Thing is that short scale strings seem to be more expensive. If you make a bass where the strings go to a tail some distance from the bridge you may be able to use normal bass strings and I think you should be able to pick these up cheaper. It may be worth getting the strings before you finalise the design. That is what I had in mind anyway. If someone thinks this is a bad idea I would be pleased to know before I get mine any further than "seeing it in my mind".
All the best.