I'm having good luck with Tom Cook's MK 30's in my SR-71.

[link]http://jetmodelproducts.com/landing.htm[/link]

The sides of the retracts are machined from solid aluminum and are pretty thick. They hold up very well, and because of their mass, don't bend under anything short of a disastrous landing.... really rugged retracts.

I've a dry weight of 66 lbs, and weigh's 80 lbs on take off.
I've had to plumb the system in such a manner to avoid as many airline 'T's as possible, by use of his distribution air manifold which works great.
Each main has 3 tires, and nose has 2. Mains in total are around 4.5 pounds each, including retract, strut, wheels, and disk brakes on each tire, all on about a 10 inch long strut when uncompressed, so there is quite a bit of leverage / load to overcome, and they do well with it.

Lance