Torque Converter and 1st gear lockup

Interested in making my slush box work like a manual mainly for engine braking down hills at low speeds. I haven't seen what it's needed for at highway speeds considering the aw4 locks up by itself in 3rd and 4th anyway but I'm looking for opinions and input on the topic.
I just recently self flushed my tranny and ended up putting in about 6 quarts of valvoline syn. atf 4 which was a bummer knowing I still got more dextron in there. I'm also running a cooler and remote filter too. But I'm taking care of it and have heard a lot of people have been running this mod for multiple years without any problems and under hard loads.
Though I've got questions about the 1st gear lockup which I wasn't sure how the aw4 reacts to not being under throttle (signal from the tps to shift) I know when your cruising down the highway it will drop into OD to allow it to roll but at slow speeds will it try dropping into 2nd or stay in 1st on a descent?

Found some more info today but still trying to learn some more, I'll read some more in depth of this one later. He does a real complicated but user friendly lock up function.
http://www.lunghd.com/Tech_Articles/Transmission_and_Transfer_Case/TransmissionController.htm
I figured I'm gonna only be using this mod for offroad since my xj is still light enough and geared decently where I can drop into OD instead of locking it in 3rd and such and also I have the 80's power and comfort switch to help slip it through 3rd and OD more if I need to.