VIOFAN is one or maybe the most efficient DF unit at he moment. Just the have a !QUOT!special condition!QUOT! in my opinion and what I could see around.
1-If you have a BVM engine like their 96 which Nelson make special for them (I think) so you can have 12+Lb of thrust.With an OS besides is a very reliable engine, it doesn develop same HP/torque as the BVM engine, so don't expect same thrust.
2-VIOFAN works with the !QUOT!rule area!QUOT! so you must have their intake and exhaust duct if you want take all the advantages of the unit.
3-If you don't plan to install this unit in one of their airplanes,you will have a long list of problems to solve unless someone will tells you what to do exactly.Due VIOFAN is very sensitive for the intake.More sensitive than RAMTEC and DYNAMAX.
4-If you are far away from the above conditions, go to JMP and you can buy the DYNAMAX which will work perfect with your OS, plus the have a matching pipe and all hardware at better price.

Remember that I`m not telling that one is better than other, just every unit and engine works better with a particular combination.
The VIOFAN is a typical I call MATCHING SYSTEM, this unit works great with their airplanes like F-86 was designed around.
I never saw a VIOFAN working properly outside one of their airplanes nor one of their airplane performing perfect with a VIOFAN and an OS. An example was one of my pals, he didn't want to pay 300$ more for a BVM matching system(engine with all ascesories) and he bougth an OS 91, his airplane fly, but all time at limit until he makes the mistake and lost all investment¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡
Other paid the extras and fly his bird for almost 2 years and rebuild egine by BVM once until he decide to change to turbines, he rebult engine again and sold it. He got the conversion kit from BVM and now his bird is going turbine.

So,be clear of what you want, if you wanna go fast you have to insure your investment, if not. go to the usual and get out of troubles, go to a proven universal matching sistem.

David P.