Having now sailed my little extravaganza I would recommend the following amendments to allow any chance for the attackers to win.
1. Allow only the Big fortification in the centre of the battle area to have heated shot.
2. If using heated shot it takes the same time as double shot to load.
3. The extra long shooting should be at half effect to allow for the inaccurate fire at over a ruler length.
4. Any transports should be armed en flute so as not to add extra fire power to the defence.

Rob.