The microtags are good for clipping the shirt back, tagging it to itself, but not very good for attaching the shirt to thr foam board. I've tried it from behing & through the board but they dont really take all that well, and from the side into the edge of the foam board. I guess there's nowhere inside the board for the back of the tag to open, a bit like anchor bolts for plasterboard, and I end up with microtags everywhere.
My issue with stitching is twofold, first I am awful at it and try as I might I can't get it straight

Secondly, I use another peice of foam board for the back mount and stitch that to the mounted shirt board. The thread itself when pulled tight cuts into the back board and I'm worried that it'll cut in more and the shirt will come loose.
I've read multiple threads on here & the grumble about mounting shirts and the advice seems 50/50 between microtags and stitching