I put this in my review of the Impulse (like the OP, I learned to coker on it). UDC should throw in a 5" piece of handlebar pipe on which to mount and protect the lever under the seat (MUni mode). The shadow kit already comes with a strait (presumably for the back but I ain’t touring) and a bent handlebar option. You could cut 5" off your least favorite one or get a scrap piece at your LBS. I’m no mechanic so I did not want to remove the brake hardware from the frame. I own two Shadow sets now and I still haven’t gotten around to cutting down either one of my extra “straight” pieces.
My advice would be to learn to ride with the handlebar in place. You dropped some serious coin on a nice kit. You owe it to yourself to learn to ride it the way it was designed to be ridden. Mine is set up (brake lever way out on the end of the curved up piece) just like the picture on UDC.
My left (braking) hand rarely leaves the handlebar. I put a ton of weight on it and my crotch (saddle pain) thanks me for that. But it wasn’t until I learned to rest my right “balancing” hand on the handlebar (to square my shoulders) that everything (cadence, speed) fell into place. Keep at it! My album has good safety gear suggestions. Live to ride another day!