The radial engine configuration offers a host of advantages, frontal area unfortunately not being one of them. The crankshaft, always being the heaviest part of an engine, is short and stiff, as is also the crankcase. This offers the potential of very high power densities. Also, theoretically, they are perfectly balanced with a single counterweight to the n-1 order (n = no. of cylinders). Unfortunately, the master-link rod arrangement that T28D talks of makes n-1 cylinders operate with an effectively ellipsoidal crankshaft rather than circular, adding a bunch of harmonics to the vibration characteristics that shouldn't really be there.
I found an interesting series of papers once on t'interweb which described the torsional problems that Wright (I think) had to solve on the Cyclone (was it?) because of this very ellipsoidal problem.
Lovely engines though.