It might be a silly question, but i'll ask anyway.

If a fork has a max disc size rating of 185mm, does that just mean for hydraulic brakes or is it okay to use a 203mm mechanical brake?

Im asking because i would expect that you could put more force through a 185 with hydraulics, than 203 with mechanical!

You might have to squeeze the lever more with the mechanical disc but the braking force would be the same I suspect. Best contacting the manufacturer if you really want to know, I suspect the answer will be no though.

No it's the same for both hydraulics and cable. Although hydros can exert greater amounts of force onto the rotor, the force applied on the fork leg is the same for both brakes!

If a fork has a max disc size rating of 185mm, is it okay to use a 203mm brake?

i realise ive edited that for my own ends, but really?