Complex sentence: Experiments were made with a pair of Il-12s towing the Il-32, but this was both difficult and risky for all involved, so the Il-32 was canceled for lack of a proper tug.
Split into simpler sentences: Experiments were made with a pair of Il-12s towing the Il-32, but this was both difficult and risky for all involved. The Il-32 was therefore canceled for lack of a proper tug.