Inspired by foamC64 i made a landing gear to my x-twin too, but a tricycle gear instead.
I used a paperclip as the axel for the front wheel, and glued both that and the rear axel with hot glue. I had to shave some foam off the sides of the bump to make the rear wheels run freely. It added about 2-3g to my plane, making it 22g heavy. It still flys very good though and both takeoff and landing works great.
I like the looks of the plane better now too, the landing gear really fit on it.