I honestly don't think a gasser is a good choice for a DP Ultimate... However, of the two engines you listed I would use the Brison 2.4. It's lighter and more powerful than the G-26 on ignition. It's also cheaper if you haven't already purchased the G-26. I recently compared these two engines for my H9 Super Cub and ended up ordering the Brison for the reasons mentions... You'll also likely need to put two elevator servos in the rear of the fuselage to balance out the heavier than glow gasser... You'll also likely want to add some flying wires to brace the tail if they are not already part of the ARF...