If you're ever really getting bummed about your size when practicing Aikido; I have the perfect inspiration for you: Sensei George Simcox.
Sadly; he passed away in 2000 (I think), but was superbly skilled, greatly respected and loved; particularly at his hometown Virginia Ki Society. He liked to say he 'had the largest one-point in North America'.
Anyway; don't worry 'bout your size; no-one else will,
just practice and have fun.