I know you said you want hand sharpening advice, however, the Guild has a Grizzly Sharpening system similar to the Tomek. Here's a YouTube video of that lesson done by Shelter Institute specifically for timber framing chisels and slicks. It takes a bit of learning but a great system.
They also use the Veritas jig for hand sharpening.
George, what kind of honing jig are you using? I find it hard to picture a chisel that is too thick for a Veritas plane iron jig, for example, which is what we use in the shop.
You are welcome to bring it by some time and I can take a look at it.
Or yes, honing it freehand is always an option. If you use a grinder first, it is pretty easy to feel the bevel accurately.
So I've picked up a 1 inch Sorby timber chisel and I have lapped the backside just fine, but it is too thick for my jigs. They don't have enough height for the blade to make contact with the waterstones. Can't find any other guidance online for hand sharpening these giants is there a trick I am unaware of?
Also is 25° still optimum for one of these, intended for hard use on softwoods