My H9 Extra has a GT-80 in it. Good for Intermediate sequence flying but Advanced and Unlimited need more. The engine fits with a couple small cut outs for the front of the mufflers. No cutouts for the spark plugs. A DA-100 will require cutouts for the spark plugs if the cowl dimensions on the new one are the same (I'm willing to bet they are). If they get the weight down on the new one, then the GT-80 would be a good choice, otherwise go with a ZDZ-80 or DA-100.