I have an Outlander, although I haven't built it yet, but I was considering doing the same thing. Just slap a "D" mm in it and if it seems a little heavy at the bottom add a little clay in the nose. I don't think that will be a problem at all. I did the same thing with my Fat boy, and I didn't even add weight in the nose cone and it flies great.
I too have an Outlander. I flew it on a C6-3 and I don't think I got 200 feet out of it, maybe 125-150 feet tops and it deployed the chute about 50-75 feet above the ground. Certainly a nail-biting experience watching that thing divebomb towards the ground.
It also needs a bigger chute. The 18 inch chute provided is too small. It landed HARD!!! Fortunately, the only damage done was to one leg housing that was easily repaired. I found that there is room in the body tube for a 24 inch chute but I haven't tried it yet.
As for D motors, I think that perhaps the D13-4W would be a good choice assuming that you stick with the 18mm mount but I think the D24-4T would be just a bit much for the legs and side tanks to handle.
I am thinking about doing a review but I want to fly mine once more because I changed the chute from an 18 inch to a 24 inch but the winds have been too strong here in South Florida to launch a rocket like that. I only reccommend launching the Outlander when the wind is dead still of if there is a very light breeze.
I'm sure sooner or later someone will post a review on EMRR. If you are thinking about buying the kit, I'd say go ahead and pick it up if you can get a reasonable price for it. My hobby shop sells them for $16.99 each, yours may vary.
I've had the unbuilt kit for over a month (next on my build list).
My method for rocket building has really changed since I discovered this forum and EMRR. Longer shock cords, nice smooth fillets, better masking, etc. - and I've made it a habit to check out the reviews at EMRR for model-specific tidbits before I open the package. This is of course, after browsing TRF for ideas and pics, gathering info to help me decide which one to build next.
So - if you ever get around to writing a review, I will definitely check it out! Maybe I'll give it a go myself someday. who knows...