I buy aluminum 20gage in large sheets and the metal shop cuts to size, lately I have been using 11 x14 and 16 x20 not cheap but I buy if for registration purposes.

This image is on aluminum and what I like is its very rigid and actually could hang by itself or on a easel and look quite nice. Palladium Base Image with Thaylo Blue pigment in gum over top, I used a low end negative to print the blue hoping the highlights would be blocked allowing the warm Palladium to shine through.
For Silver printers who are use to toning , specifically exotic toning , this method of working is very compelling and liberating for ones vision.
All my Alt work is on aluminum as I do duo tones for most of it, I am not sure if I would start mounting Silver Prints on aluminum
I have considered this ( to mount the silver paper in safe light, quite easy proposition actually , then make the silver print as normal, and try
alternative print methods over-top, I think the hard part would be making the registration negatives to fit, an idea that maybe Drew could put his thinking cap on and explain how I would do this... exact registration now Drew , not close enough for govt work.
This would allow for the incredible Dmax and Contrast of Silver with the extended range of pigmented gum for effect.
Today I am going to put old screwed up alt prints that are mounted on aluminum into really hot water to see if I can strip the prints back off the aluminum and reuse.
If it works I will be a very happy camper