Jack
I learned the hard way a while back that there are several things different about SQ2 lugs compared to Designer lugs.
The APS is one thing. I posted a video with an explanation and a work around, here. If you are replacing Designer lugs with SQ2 lugs, if your Designer APS parts are still usable, you don't need to worry about this, they will work perfectly with the SQ2 lugs. If, however, you are replacing SQ2 lugs with Designer lugs, you will either need to buy the current APS parts, or modify the Designer APS. Consider the condition of the APS pieces when deciding whether to buy new, or modify. Lastly, and I certainly don't recommend this, you could open up the holes on the SQ2 shell to accept the Designer lugs. This could lead to alignment issues with the lugs, plus you will have to take extra steps to ever use the current APS pieces on your modified shell.
One MAJOR consideration is that Designer and SQ2 tension rods are NOT interchangeable as they have different sizes and threads. So, be sure you have everything on hand, and test fit it all prior to make any mods, particularly mods that can't be reversed.