With only a 20% duty cycle it better work like it says. 20% duty cycle mean you can only use it for 12 minutes/hr. Since the MV50's are 100% duty cycle, I would save your money and buy 2 of them, set one up and keep the other as a trail spare, or set them both up if your alt. will put out enough juice. If you have them in an enclosed just run a cooling fan from Radioshak(about $25).

More than tread lightly. Leave it like you were never there, nor anyone else.
'90 X-cab 4.88's 33 BFG AT's, rr ARB, Headers, Ignition upgrade, cold air induction.
'91 X-cab 5.29's 315's BFG MT's, rr ARB, custom bumper and flatbed