I have just purchased an Ampeg SVT-15E, which is on it's way from Florida as we speak. Being about to own this cab brings me to an obstacle I have been thinking about for a while, and will now have to act on. The good: I will be stacking a 410HE on top of the 15, and making a gnarly fullstack. The bad: The top of the 15 has the metal cups for stacking, but the bottom of the 410 has castors, which will not work for stacking. My planned solution is to put some stacking rubber feet on the bottom of my 410. I believe the feet have different spacing than the wheel castors, so they won't overlap. I actually don't have my amp with me so I can't check (it's at my house and I am at school)...can anyone verify this? Would a cabinet need a different feet arrangement than that of an amp head since it's so much larger? The way the cups are placed on the tops of Ampeg cabs looks designed for heads, since there are two in the front and two in the middle of the cab. For stacking another cabinet, the cups seem like they should be at each corner of the bottom cabinet so as to give the most stability. Is this correct, or would it be stable enough as is? Do they sell those feet anywhere? I found the round rubber feet (which go on the bottom of the cab in the corners) on ebay, but so far have yet to see the tall stacking feet anywhere. If they're not available, I guess I can always buy a similar product at a hardware store or something. Regardless of what I do there, I do not feel comfortable straight drilling into the bottom of my 410. Does anyone have experience with a mod like this? What precautions should I take when attempting to mount the feet? What screw length would be appropriate for this? (I guess I can look at the screws on the bottom of my 450H head, which has the kind of feet I'm looking for) Is magnetizing an issue when working on a speaker cabinet? Or, is there a better way to stack my cabs which would not involve modding one of both of them? Any help here would be hot.