Is that board a Delta?

I bought a whole pile of gear of a guy called raodzie out your way. had this custom board made for himself years ago said " only use it when it Nuking". mast track is backwards on it Think it was a custom for when he used to surf down south. Ripper of a board good to see people still using them besides me !

Gona pick your brain for a sec !....
What size fin do you use on it stroppo? only thing i have used is a 21 weed wave but the front end sits high in the water. Even with the mast fully forward cant get it to sit level to get the rocker working. Im not sure if that's how its supposed to sit.Or weather a bigger fin would make the board sit more horizontally (push the front end down) Or if the fin is to large and making the board sit high in the front end.
How come they make the mast track backwards?