I think Steve uses one on his 29. I used one briefly on my 29 (I'll see if I can find it - if I do, you can have it). Drilling would obviously be better, but that doesn't look like an option at this point. I remember it being ok, but I had a aqualifter to ensure the siphon never broke. The eshopps one is pretty popular. If you do decide on that and need a sump, I just got my new one, so I have a 20L (30" long i believe) with baffles and everything for sale. Was just going to post it actually. Has a little wear and tear, but still very good. Currently soaking in vinegar.
In my opinion a sump is one the best investments you can make for the longevity of your system.