Sartorikid,
It looks like the only place you could put that bracket is on the port side but you said some thing like a live well there I think.I think you could attach it but you might want to talk to a dealer who has worked on that type of boat and see what it would take to get to that part of the transome you have to get there to bolt the bracket down with thru bolts.It doesn't look like an easy job but I do belive it could be done.By the way nice rig!! Good luck and keep us updated if you decide to do it.As far as your 250 goes if its a 4 stroke you could probly get down to that rpm but you will lose some of your boat control going that slow.What I mean is you will not be putting out that much thrust so it won't be pushing your boat like it would with more rpm.I hope I'm saying that right so you could go with trolling bags but as ilucas has said they can be a pain but they are use all the time in the great lakes trolling for salmon.But that's another whole thread.Hope this helps.I'm no expert but just my two cents.
Come spring when it is out of storage I will be able to look at it and decide on what will work best. I may even go with the minn kota engine mount, it has 202 lbs of thrust and is rated up to a 26' boat, we'll see.