I have 2, one with a contra and the second with a Pletty Advance.

T-can should be zero to the stab. +.7 on the wing is what both of mine are set to. Just a little variance to take out aileron trim differences

The nose ring started at about Neg 4 deg. But for the contra i trimmed the nose ring to 0 deg

The Pletty started at about neg 3 when I mounted the motor.. Another friend has one as well and had told me I would need to put some up thrust in it.
I have since shimmed to about neg 1.5. This aligns with the info you were provided.

If you are worried about making mods to the nose ring I would start with a tapered shim behind spinner when you mount the fire wall, and start
at about 2.5 deg