Those trim tabs with the water pickup built in them aren't very good.My first boat had them and very little water was coming out the side of the boat. Get a rudder system with pickups in the rudder, as they force more water into it. I also bore out my water fitting to 1/8" or get larger id fittings and use 5/32" water line from Zippkits
XL Silicone Water Line 4 Feet Model Boat - $4.00
Get all water line fittings to match the large water line. Zippkits has rudders and about anything you'll need.