E-mailing him at
cohhcarnagetwitch@gmail.com is a good way but honestly just contacting him and asking him during his live-stream is likely your best bet. Or at least, e-mail him and ask if he can check his e-mail for you once his stream is over.
Another way is to leave a thread with your ideas in the Sub forums section as he does check there every once in awhile too

Sometimes I'll pop my head in to chat...