Bob, excellent videos and post! Here are a couple of things that may help. I agree that the steering is a little slower to respond and is harder to manipulate. Some of this must have to do with the extra friction of dual controls. I didn't notice it nearly as much on the test boat with the rudder knob -- it adds a lot of leverage to the rudder control. I'm not sure why it isn't standard equipment.
As set up, the TI has the same sheeting leverage as the AI. With a 50% larger sail in those winds you were sailing in, hauling in the sail is definitely a two-hander! You have the option though of improving the sheeting leverage, but the penalty is slower sheeting and single cockpit control only. I didn't try it in this mode, but it shouldn't take much time to convert if you're planning to go solo in high winds.
Sorry you didn't get a chance yet to try out the rear cockpit solo under similar conditions. I think you'll find it to be drier and it should improve the handling of the boat as well with much less of a spin out problem -- rudder stays in the water more; fins aft add lateral stability; weight aft gives better rudder response IMO (although it can still be twitchy st speed). I felt the boat was quite nose-heavy soloing from the front seat. It'll be interesting to get your comparison from the back seat solo!