Dick, since you're here in the 1/2a forum, can I assume that a 1/2a engine might make an alternative?
www.coxmodels.com has the Surestart Cox engines like those on the toys for seven bucks each! I know you like to scratch build, so look at one of my plans to get an idea of the size and weight that you want for good performance and build one from scratchquicker than you can build an electric ARF! (my site is
www.ulmer-rc.com ) Not sure if this is what you want? PM me your address and I'll send you an engine and plans.