I am running a NGH GT17 gasser on a 60-sized Pulse XT right now. I even flew it today. It is a very nice match.

Jamesc43 is definitely right about the prop size. Iam running a 3-blade 14" on it with slightly taller than stock landing gear. Ihave some larger 4" wheels that I'm considering putting on the plane so I can use a larger prop.

While the GT17 is only 3cc's smaller than the DLE-20 (which I also own), I believe that the DLE-20 is much more powerful and I believe heavier. Even with a 2300 mAH2S A123 battery pack as far back under the wing as I can get it, the plane is still nose heavy. And that is after I cut out the lite-ply webbing behind the landing grear (which is also below the cockpit) to move the fuel tank to the C.G. (which included removing the stock 14oz (?)fuel tank and replacing it with an 8oz tank) and a fair amount of lead back at the tailwheel.

Here's your primary challenge:
A large enough prop that you don't over rev your DLE-20 and yet small enough that the prop isn't mowing the grass or grinding down on the runway
Not tearing those big wings off when you go WOT - the plane was not designed as a racer
Reinforcing the fuselage so that the vibrations and power doesn't tear it apart - Particularly in the original fuel tank area (over time I've done a number of reinforcements and repairs)

Don't get me wrong, I really like the Pulse XT. It is a lot of fun and flies really well with a small gas engine. But it flies best at modest speeds.

I even have a DLE-20 on a Ultra Stick 60, so I'm not shy about putting some power on small airplanes.

Have fun,
Paul


BTW - I think James was refering to the Pulse XT 120. I think that would be a good match too. I seem to remember that some people think that the tail feathers on the 120 are a little weak. I'm sure a search would turn up the specifics.