Canadianmade wrote:
1.Flat bottomed strut creates lift so is good on hydros cats etc.
2.Skeged strut usually used on cats or flat bottomed hulls like cracker boxes etc it helps to stop the hull slideing as much in the turns.
3.Extended is to get the prop further behind the transom into clean water and also effectiveley makes the boat longer

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4.Running the strut through the bottom of a hull is normally done on cats or hydros in particular the latter,this can sometimes help with turns and handling as i understand it but you can lose a little speed.Quite a few thunderboats use this method.
5.Strut height effects how a boat runs ie wet or dry stable or loose etc, altering the angle will alter ride attitude either nose up nose down etc,also altering rudder angle effects ride attitude more than you would think.I never use trim tabs i use the strut and rudder to trim all my hulls

.Does this help Pete.If you search for a book by John Finch called ADVANCED R/C BOAT MODELINGit will help you understand what does what.
Mart