I have the BME in an Midwest Extra...beam mounted. I didn't have any problem with the beam mount at all. I took a GreatPlanes 1.20 size(the adjustable one), glued it together, so it was basically a one piece mount at that point. Then I simply cut it directly in half, cleaned up the cuts on a belt sander, and had 2 perfect beams to mount the BME. Very easy to do, and lightweight, and absolutey no problem as it was very familiar to do that way...for about $6.00. So don't let the beam style mount detour you. I can say that the BME is a very good running engine, it's been in the plane for about 2yrs now, with no troubles at all. I've got about 7gallons of gas through it now, so it's just coming around nicely. I can only imagine a DA50 would run as good or better, and by reading these posts, I can say you probably won't go wrong with either one.
Either one will require a battery pack and switch harness of some sort though. Also a muffler that isn't included. The pitts-style runs right at $100 for the BME I think.
For a battery pack, I use a 1400Mah ni-cad, with a standard futaba switch harness wired onto the electronic ignition module. Thereby letting me charge the whole airplane with a Futaba style connector.