Mike, I second that. A 90 is very big for the Corby. I use a Magnum 70 and have ample power. Mine is mounted horizontally and fits within the cowl entirely.
I am at a loss to explain why the Corby isn't more popular than it is because everyone at the flying field comments on it and the quality of the kit is excellent.
Anyhow, it's their loss ..... I might buy another one to set aside for later ..........

Ari