Right, went to the hose shop today, and got everything bought and made. He had all the parts in stock for it to in theory work. Was NZ$400 in total, and the whole splitter cost me only a bit over $1K, but that's the cost of doing things properly I guess. I really don't want this to leak or split.
The 90 degree swivel fitting on the loader valve works well and there's plenty of clearance. We stacked a 3/4-16 UNF straight fitting with a swivel, but it didn't add too much height. I had to go find a copper compression washer to seal it, which is what the hose guy recommended - the fitting didn't have o-rings.
The fitting on the transmission did not work. This has only 45mm clearance under the seat, so no room to stack two pieces. He had a BSPP 3/8-19 90 degree fitting, but it's not a full swivel - it won't rotate the full 360 degrees. There is a casting on the top of the transmission that fouls it, so I can't screw it in. Back to the drawing board on that one - he can order in a banjo that will fit then an adaptor to fit the hose we made. He had some concern that the banjo was too low, and the hose fitting then wouldn't screw on (it's larger diameter than the banjo height). But if I route the hose just right there's a gap in the casting where I should be able to screw it all together. The transmission already had a copper compression washer I can reuse.
All in all, I think it's looking very successful, but waiting on the new banjo that he's ordered to be sure.
I'll provide some photos once done and working, in case someone else wants to make this modification.
