Hi:
I have 4 ryobis,later I get a 25 cc gasser and found it heavier than the ryobi.i worked in my own conversion kit ( prop hub, new muffler and very lightaluminum mount and it weight 1.200 grms. included the plastic 18x10 prop),so may be the sst 2300 and the ignition would be around that.
The ryobi with standar magneto and flying wheel was at 1.380 grms, already converted.
But for 71" WS, I think the best would be a 2 or 4 stroke 120, if te airplane is light it would need few rpms to fly and do some aerobats so there would be no such fuel consumption.

But gassers are so cool!!!

It´s up to the customer.