Yeah, I've been thinking about giving this a try as well. I'm probably going to order this bit on Amazon, and attempt a double mill with 7/8ths first, then follow up with this. It will be interesting to see how even I can get the two seperate plunges.I think you are talking about the 27mm t-channel (wood working) bit? The issue with that bit is it is sharp on the edges and the center "rail" (for lack of a better description) on the bottom has a gap. Theoretically, you could "double mill" (7/8" and then the 27mm) to git a flat bottom but I don't believe anyone has tried it.
I did order the 27mm (on eBay - Chinapak) to try it for myself.
https://www.amazon.com/dp/B07QB3FPM...olid=1O2VS2N1R7OVZ&psc=1&ref_=lv_ov_lig_dp_it
I've also had a discussion with another member here who knows someone in the tool and die business who may be able to fabricate a 27mm / 1 1/16th bottom cleaning bit.