You are going to need long shaft motors, I would strongly recommend an outboard bracket, it works very well, doesn't seem very popular on your side of the pond and from a functional, practical point of view not using one is shortchanging yourself and the boat. One, you can tilt the motors ALL the way up out of the water with a bracket with no clearance issues, without one I'll bet you'll have problems. Two, if you ever have problems out on the water a bracket gives you a relatively stable area to troubleshoot problems from without leaning out over the back of the boat, a huge advantage. Three, the bracket increases the effective length of the boat (rarely a disadvantage) and imho improves the performance of the boat due to offset.
As to setting it up I could probably give you some pictures and some measurements regarding motor installation, it might help, I am sure there are others on this forum who also can add plenty of input. Good luck!
I hate to be the lone voice of dissent but I think you may be too short on your
motors. I think they'll work but you might find those power heads closer to the water than you'd prefer. My boat measures 28 inches from transom (bracket lip) to keel, I have about 10 inches of clearance with the waterline at the stern. that may seem like a lot but when the boat is pitching and the motors are hanging off the back it's just enough to keep the powerheads up out of the water in most sea states. 25 may not be enough length on your boat, I hope it is but from my point of view... I don't know... Look, if they are too long raising them five inches is hardly noticed, if they are too short, what do you do?
I have 30 inch shafts on my motors.