24mm is probably better, though we could always use an adapter. I'm not sure if E2X makes sense, it would be easier, but doesn't teach as much building technique...
During the summer of 2015 Claude asked me to help at a build session for foreign high school students. We used Flis Thingamajigs and Whatsamacallit. It worked out great. Both those kits use the Flis patented interlocking fins. One of the kits use streamer and the other a chute. I prefer a chute unless you are launching at a small field. Flis kits come with excellent directions. We used B6-4 engines which you can buy in bulk. We launched at the Acton field. Check out my latest Torrent post.
