I have to chuckle whenever I see my fireplace show up in a thread... it was one of the FEW times I actually could justify lighting it up here in Florida.
Still have that Humbug hanging in my 3rd bedroom as wall art. It is surprisingly well finished and still in great shape. The stab is huge as you can see by my yardstick laying behind it. I bought it from Tom Dixon at a KOI shortly after Bob passed.
Of the large Humbugs, I think this was the last and best of the bunch, and it flys great. The plane fly's very conventionally, which might make some people scratch their heads. It was originally set up for an FSR, and it was under-powered. He switched it over to a ST60 and it was pretty good. I had a ST56 V case in it (I have no idea why, I had plenty of ST60's at the time, but it seemed like a good idea at the time? I plead temporary insanity)
I may revisit the plane and stick a fresh ABC ST60 in it, or my Casalles Randy Aero ST 67 in it, because the only real problem I seem to remember is that it was always searching for a little more power. The weight is fine, it is just a huge draggy plane. The wing is basically a Patternmaster wing with the flaps permanently attached to the trailing edge.
I have a side exhaust PA61, but the dimensions aren't even remotely close, which is too bad, because I bet that would be THE answer for this plane.
PS: Owen Richards who sadly has long since passed, was a local club member and had the Orange Humbug for a while, on loan from Owens son who lives in Georgia. Owen never warmed up to that plane. He tried trimming it 9 ways to Sunday... pinned the flaps, with flaps, moved the CG around, just never got it to turn a real corner.