I bench ran my WREN MKIII kit built engine 3 times since it was my first turbine and I followed the recommendations in the owners manual. Doing this did give me some training on proper starting etc. I just got a Super Sport and put that right into an airframe ( FLASH) and started that in the plane, only adjustment was a slight tweaking of the propane flow valve. I believe there is some merit in bench running for anyone who is new to jets but only for a few times to learn the start up procedure etc...AND it is not necessary to let it run at full output for long times on the bench...