Sorry its been such a long time since my last post on this subject.
I did make the transom taller by 5 inches and it transformed the boat from running with a longshaft on a short transom.
The steering was improved the splash comming over the back was crazy with it left down too deep.
speed increased from around 18 to 26mph and the boats attitude was also improved greatly.
Time to plane dereased by about 30% as well.
overall the boat was dangerous with it too long,i found steering very hard to keep it under control properly,but like said above its all better now.
What i done was to fit 2 3inch x 3inch lengths of angle to the inside of the transom and fit a board or same thickness as transom directly above the top to raise it up.
This was then covered at the back by a simply piece of ply all over the rear of transom for looks as well as a touch of strength.
overall it worked a treat.
pics below to show what i did.
i no longer have the avon and have now got a rigid orkney dory to give me a touch more room inside.
The avon was a good boat and done exactly what it was designed to do, a very good boat to own if your need a boat that can be packed into the boot of a car and can go anywhere you want it to go.
It wasnt what i would call a dry ride, but very good fun boat and could take a real good pounding that i dont a rigid boat could take without doing damge.
Would i have one again..........yes .
Thanks to those who wrote on this topic,it helped me decide to raise the transom and do a few experiments i would not otherwise have done.
keep it up (no pun intended)