I'd get a different prop before strapping a trolling plate to the bottom end...
If you are down to 1.6, it doesn't seem like you have much work to do. A flatter pitch prop would do the job for sure.
that's my solution ( different prop), I've used trolling plates, and meh, not the best answer,ive done buckets, again meh.. I have a sea anchor that is a great tool.... different prop works well, pop in and out of gear on occasion, to vary speeds, it's better on the engine as well, a small kicker is the best solution, but honestly never had an issue with my 115 trolling for salmon,if I need to a crawl I use the electric..
I have a spring loaded EZ troller on my 18ft Crestliner with a 70hp OB and love it. I got a tip (maybe here) and added a notch at 45deg and that helps retain boat control... but my opinion is that at <2mph how hard is it to control a boat in the first place... I did buckets/driftsock for a few years.. IMO trolling plate is far superior