With regard to the RUM issue, there are a couple things to take into account. The first is that 89 (or more) grains is a lot of powder (gas volume) to suppress for a can built around .308, or about 1.5 by about 9". For comparison you can make a really effective .338LM can that is about 1.75" x 10.5" or so. The difference in internal volume is relatively large. So outside of everything else when you get into an amount of powder than is close to what .338LM uses, you probably want a can about that size for good suppression levels.
The second issue is that whenever you have a cartridge that is more overbore, the pressure at the muzzle is higher. So if you designed a can for 90 grains with a .338 bullet and gave it a certain safety factor, if you were looking at 90 grains of powder and a .30 or 7mm bore, the muzzle pressure would be higher and with the same safety factor it would have to be built stronger, IE, heavier.
Our heaviest duty can right now is the 223A which was designed around extreme firing schedules on 7" M16's. Take a titanium precision rifle .223 suppressor that weighs maybe 1/3rd or 1/2 its weight and try the same thing and you'll have catastrophic failure eventually.