I have both a ringed one and a lapped one, and they run slightly different. I run about .035" to .040" head clearance on both. Ventura about .290". and a 5 oz. tank for the ringed one, and 5 and a half oz. for the lapped one. This should be plenty for the old time pattern on 10% nitro. I have tried several different props, and my Viking likes a 13-4 wide blade APC with the ringed one running in a 4 stroke with just a little break. On my Humongous, I run either a 12-6 or 12-5 APC or Zinger. Sometimes a 13-6 works also. Just think of it as a big Fox 35 and you will be fine.

The Humongous is a pretty dragy plane. I have found an APC 13-4 wide blade works pretty well most of the time. You might want to give it a try. If you have the stock spray bar needle in yours a .300 ventura might work OK, and if not the panty hose would most likely do the trick. I have had good luck running a Fox long R/C plug in both of mine. Oh, after it gets broken in it should run a really nice 2-4 break with that 13-4 APC.