I can thoroughly endorse GDI Products. I've had multiple cross members, outriggers and other useful bits of kit off them over the past few years. Everything has been well priced and above all fits! A lot of what you get from other suppliers seems to come from them as well. More importantly, they are always very helpful and efficient.
The only issue I had was a problem with Lightweight bulkhead outriggers where the mounting bolts were 5mm in board of where they should have been. Turned out that the data supplied to them was incorrect. If the outrigger is welded flat on the outside of the chassis rail, the whole is only 2.5mm out, so not obvious. If you let the outrigger into the chassis rail, you lose that 2.5mm plate thickness and end up with a tolerance stack of 10mm across the vehicle if replacing both outriggers. I ended up letting 5mm into each outrigger to compensate. If anybody is contemplating chassis outriggers on a Lightweight, I posted the finding on the military lightweight club forum. Might save you a lot of time and bother.