Geoff, most of your questions are answered in the last post, but sad to say I was given very bad advice and ripped off by a model boat shop when I started this project. >:(
I had no experience at all of anything smaller than "an accumulator"
other then AAA duracells.
I've been on a very steep learning curve with this hobby, and most of my useful learning has been on this site.
I've now arrived at the same conclusion as you, and I quote a motto that has always stood me in good stead with life and petrol engines...
"theres no substitute for cubic inches"
I'm almost there.
