T-terminals are notorious for failing with little to no warning, even when oversized. Something which has been common knowledge amongst racers for several decades. A trait of note that often draws comments to such effect (unsolicited ones). Such as when I called Brion Toss, & several other riggers of note, when trying to track down some fittings for Ann & Jim Cate. Though this characteristic wasn't news to me, having seen several fail over the years. Usually in the region in the fitting where Ann & Jim's did.
I'd suggest reconfiguring things in the standard setup. Where you have a compression tube welded transversely into the mast tube, & add a doubler plate overtop of it. In order to beef things up to account for any weakening of the aluminum
due to the fasteners, compression tubes, & welding strength losses.
Followed by hanging a tang off of an oversized bolt placed through the compression tube. And then adding a conventionally toggled stay, configured with mechanical end terminals.
There's an example of a compression tube & doubler configuration at the Cal40.com website, here http://www.cal40.com/files/TEMP001.pdf
Plan B would be to use some of the Dux tangs, & their synthetic rigging.
Though if you have a few days/a week to spare, pick up Brion Toss's books
, as well as a few others on rigging. So that you can evaluate a few more options, even if some of them might be a bit retro (& often cheaper). To possibly even entertain poured sockets. About which there's plenty of info in lots of non-nautical locations. Though Ross Norgrove penned a good section or two on their use on boats, along with older wire types