Sanders, the 101/4.5 Ektar was offered for 2x3 Graphics in the Synchro-Rapid 800. There's a picture of the lens in that shutter in The Bible, 10th ed, that shows no "T" setting and no blade arrestor.
So you're SOL (no relative of LOL). Use a locking cable release. There's one in the picture in The Bible that I mentioned, and that's a hint.
If you're bound and determined to hang a 4"/4.5 tessar type lens in front of your SL66, 101/4.5 Ektars in Flash Supermatic and 101/4.5 Raptars in Graphex/Rapax (same shutter, different engraving) not attached to cameras are fairly easily found and much less expensive than those attached to a camera. Thing is, my tests, both formal and informal, found that the 103/4.5 Graftar in Century shutter is a better lens than the 101 Ektar, so you might want one of them.