Not trying to spend your hard earned $ but, since you have a kicker, you might want to consider one of the popular electronic throttle controllers. I too struggled with troll bags (21β boat) and use them primarily when the water is very rough as it helps settle the boat in the waves. I set up a Trollmaster brand throttle controller on my kicker and it solved my trolling speed issues. I can fine tune my Troll speed all the way down to .8 mph. You donβt need to have kicker motor controls up front, just the small electronic module that is part of the Trollmaster, or I-Troll, etc. of your choice. It also makes life considerably easier if you have an EZ Steer or similar type connector rod between the main and the kicker so you can steer the boat in the usual fashion.
Hope that helps in your decision making!