Question re: Aftermarket Coil for Teknetics Greek Series

I have been considering getting a smaller coil for my Delta 4000. Teknetics sells one. So does CORS (formerly NEL) I think there may be another few out there.

Does anyone out there have any experience with an aftermarket coil for the Teknetics Greek Series (Alpha, Delta, Gamma) machines? Which one did you get? Did you like it?

Any input appreciated