My preferred method is zip ties. I have used rubber bands in the past, they work, zip ties give a better connection. I use 1/8 inch ones, they will allow the gear to break away if necessary. I use the wide craft sticks, one on each side of the foam to distribute the loads from the gear.
If you are done this is a little late, Use it on your next one. I add a wide block inside the wing with bind nuts. Bolt on the landing gear. I had this on a Mig 3. Spitfire, and Mustang. I do add some glue to the bind nuts. Glue the cut paint stirrer in with epoxy.