Heres my effort at going fast, an old MDS 38 with a 10x6, used to keep up with any MVVS 40 speedster.
low drag was the idea.
deltas have a couple if disadvantages... first, to hide the gear they have thick roots, which taper all the way down the wing = high drag, my own design delta had thin wings and a fuz, up to 30 mph advantage over any other plane at the field on the same engine.
Second is the symetrical deltas have to fly at a AOA to get lift, this leads to vortices behind the wing and slows it down. Flat bottom sections cure this.
There was a post ages back im trying to find again where the perfect design was discussed.
I've got a few ideas in my head that time and money allowing should lead to something really diffrent and fast