RE: Vagabond Problems
I had one of those All Star bipes. Great flying plane. Talked with a lot of flyers who had trouble getting them to fly. They were surprised to find out I was taking off grass with an HB 15. Everybody I talked with who had problems were using engines in the 19 to 29 range. Way too much power. In fact, I had drilled my mounts to fit either the HB or a Fox Schnuerle 15. They were the same width, and the mount only needed 6 holes. After talking with a number of people who tried the plane with the larger engines, I decided to stay with the HB. 12,500 rpm on an 8-4 prop was perfect, the 14200 or better I was getting on the Foxes would probably have been too much power. In the original RCM article, the designer talked about takeoffs from hard surfaces with as little as 09.
As far as Dutch Roll under power with old timers, when they get nose high under power, it's sometimes a matter of the large wing blanking the tail surfaces at high angles of attack and causing partial stalls. I had this problem early on on a 72" Spook 72 with a K&B Stallion turning an 11-5 prop at about 10500 rpm. Added 3 4-40 wahers under the rear of the mouning lugs. Old FFers would usually correct this with engine down thrust, even with the old engines turning big props at what would be fast idles on our newer engines.