While I'm a tone junkie, I wish I was so sensitive that I could tell the difference between a rectangle, round, oval or square opening on a cabinet.

I'm sure it does, but from stuff I read, size of venting ports have the biggest impact. The bolt and rectangle share the same approx. Sq. In. Opening. I hope that is enuff.
These JBL came in a closed back Bandmaster cab. Even then, they had that jangle sparkle. I think all will be okay.
The cab shipped yesterday. I did get it already but had to send it back. The rear bolt just didn't come out right. Looked more like Charlie Brown's shirt design. The front baffle wasn't mounted deep enuff nor were the wood spacer blocks tall enuff to clear the HT EBay clamps. This is okay as he had specs to other clamps that didn't share the exact HT specs. And I blame the SYF design fault mostly on me. I should have provided a lot of pics and been clearer. I wrongly assumed he'd know what the 13pt bolt is.
But Tim was amazing. I mailed it back (BTW- parcel post ROCKS!) and he took it back and made it right. Kudos to him. This is the first he is building with a direct HT design, and the first with a crazy bolt opening. I'm happy to be the test bunny. Its best to work out any issue now so if anyone orders another like it or close to it, he's got all the specs right. This is the first one he built in the 13ply all baltic birch plywood. So its a bit of a learning experience. I told him if he makes the full 13ply HT-spec with cover available at the price point he sold me mine, there would prolly be many others beating a path to his door.
The overall build quality is impeccable. Dovetail joints! I was amazed by the craftsmanship he has. On pare with the best Amish kitchen cabinets I've seen. I expected the rear bolt design to be a 2 pc. panel as it would be easier to cut out.. Instead, he cut the bolt out of 1 piece. That took a lot more time and was a sign that he wants the best he can do. I am certain he got it right this time, and I will not hesitate to recommend Tim (besides, he has the coolest first name next to Jerome).
For the price ($189 shipped), it may be the lowest cost for a semi-DIY HT-style cab around. The plywood would have cost me more than half of that, and would have came with the very distinct possibility that I would fuck that shot all up.
Will post pics when it arrives.