The H17 shares the same rudder as the H16 and maybe others H18?. BUT the pivot holes differ. Maybe your rudders are from another boat.
The rudder blade
is the same on the 14, Wave (not the EZ-Loc blade, though), 16, 17, 18, Getaway.
The 17 shares rudder castings with almost everything except the 14 and 16. The rudder castings determine the hole placement in the rudder blade.
While the upper, aft hole is in a similar location, the forward holes are so different between the 16 and 17 pattern, it's doubtful you could even fit the blade to the castings with mis-matched blades.
From what you've described, you've got rudder cam problems, and your rudders are not locked down.
Tacking the 17 is easy - once you get the technique down. Steer gently - and consistently (don't let go of the tiller in mid-tack). You must
ease the mainsheet in mid-tack - probably 4 feet of sheet at least. Make sure the mast rotates. Don't start sheeting in until you start moving on the new tack, then pull it in slowly as the boat accelerates.