SpudFiles

I use 64 layer alu. foil disks in unmodified unions, but I don't think that you would have much luck trying to cut aluminum much thicker than that without sheet metal cutters, and you'd have some butt-ugly disks then. For 11x in a 2" union, you'd be looking at over 100 layers. Which would mean about 8 disks from a 100' long roll of 18" wide standard foil. Which likely isn't practical at all.

I got a high pressure rated forged steel 2" union from McMaster-Carr yesterday, and if the small tapered area was machined flat (which would be a very simple operation) you could make a copper/brass/lead gasket and use steel sheet as disks.

And I'm not planning on using flanges on any of my current projects because I haven't found any rated for more than 2500psi at the moment. If someone could direct me to a suitable 3" or 4" flange with a rating of 5000psi or more, I'd greatly appreciate it.

@Spudfarm: your hybrid is going to have a very poor reload time anyway, so it would likely be beneficial for you to just go with a flange, which would allow you to use whatever kind of disk you wanted.

i may make a flange if i don't get up with something else. so can you to get one high above 5000psi rated. i will cut the barrel in half near the chamber and weld on two 1/4" steel plates with bolts to make a flange

I once saw a guy who used some sort of bolt action load to put burst disks in. I dont remeber how it was called, but he achieved a very high ROF for a hybrid.
Though that will probably not work with the pressures you are using unless done perfectly.

if anyone has seen the connection on the barrel on the hybrid that is what i think of but not with tose locks, i'll use screws