5 rolls of film to make a short? Thats about 15 minutes of raw footage. You're gonna need more.

Plus before putting the film-cassette in the camera, shake it well.
Over time the film can get a bit stuck and your material can look very jumpy.

For more sharpness and less jitter get this small pressure plate
http://www.super8.nl/english/e_rent_s8plate.htm
Its worth it!

So whats to big difference between the BM 2.5K and 4K cameras? (besides resolution ofcourse)