I have a wii u pro controller as well, and a wii classic Pro controller, not sure if it has analogue triggers on mine, I'll check at the weekend. 3rd party wii u pro controllers are under £10 on Aliexpress.
i enjoy off-tv play too, infact i don't even have my wii u connected to a tv anymore. i've actually used the wii u injection app to make Mario Kart Wii playable on the gamepad with gamepad controls. im considering a wii u pro controller, but think its quite pricey at £25 for a 2nd hand one. have you tried the wiimote and classic controller combo, that has analog triggers.
I have an adapter as well but haven't had much time to use it yet, also annoyingly you need a wiimote to be able to use another controller, I have one but again haven't got round to it yet. On Sunday I'll try use the GC controller adapter and also a 360 controller (unlikely I'll ever use this but science). Controls are OK, but no analogue triggers is a pain (sunshine more than most other games), but they built in a half press method. Probs better with the GC controller but I love been able to watch TV and play in the gamepad.
how do you find the controls (button mapping)?? not just for mario sunshine but other gamecube games. im considering buying a gamecube adapter for it. i was playing mario strikers and found the controls quite awkward
Awesome! I've not read loads on it yet but I take it you put Wii games in some kind of bubble and transfer them via SD, as you have to for Wii U games then?