Jim_MI...Very nice set up and the Scotty Depthmaster is an excellent unit. I know from my experience its a workhorse downrigger. Reducing the arm length is the best way to keep the weight close to the hull and improve tracking.
I used this exact model for a couple of years until I decided to try and adapt, my older 12 volt DC, Cannon Mini Mag, to my 2013 PA-14....all I can say is the electric down rigger is the ultimate solution if you can afford it.
In my case, the Mini Mag was on my old 18' Jetcraft boat and I removed it, when I sold the boat in 2009, since I was not going to get the real value of it back in the sale......so, it sat in my garage until last year. Then, I thought that maybe, it would work on my PA-14.
My only extra investment was an 18 Ah battery to drive it......the $50 investment was a really good choice in the end.
If you exercise the down rigger frequently beyond 50', all I can say is the electric model is "really nice"....especially when you have a big fish hooked on!