Hi KOI
The Hobbyking strut/rudder unit is part no. HK-502B20 with 4mm Threaded driveshaft(62mm), 4mm drive dog (HK-518B20), 4mm Teflon drive washer(194000026-0), 4mm x 300mm flex drive shaft(HB510B30), 5mm inner shaft sleeve 310x5mm(194000028-0) and 6x300mm brass tube(HK-514B15) and turn fin set (194000016).
I had to add a small block of wood to the transom because of the flex drive length and to get the battery in the bow pass the motor.
I used the water cooled ESC because it is lower than the car ESC's I use.
Brass tubing thru the frames with 2.5mm silicon fuel tubing(OR005-00601) for the flexible connectors.
I also add lead weight in the front sponsons to get the CG forward as I move the battery backwards and forward a bit.
Can-a- bus