RE: what is the best delta?
Once the momentum of a real fast spin gets built up the rudder has to be stationed pretty far away from the CG to be able to stop reliably it.
The Lil Toad was my 1st delta and is a RCM plan from the late 50s or early 60s. The local know-it-alls pronounced it un-flyable when I showed the skeleton at a club meeting. One guy said that there were very few model pilots in the USA capable of controlling a delta for a full tank of gas before crashing. Some said that the airfoil had to be thick and reflexed in order for their to be any hope of flying. This kind of talk was going around in 1989.