Jace's reply ( an inch to an inch and a half sounds about right to me .You can also cant out twin installations with the legs out from each other . I understand that one South African Cat RIB maker has them canted out by as much as 20 degrees !
One of the bits of advice I always give to first time buyers is to buy the boat , engine and trailer from the boat manufacturer , who is the person who knows best how to hang an engine on his hull and how to set up the trailer . The boys over here in Lencraft have turned engine hanging into an art form .I am sure that most other makers are just as good on their own hulls .
You can always rectify pull by adjusting the engine trim tab ( also probably the anode ) to point slightly in the direction that the boat is pulling to with hands off of the wheel . i.e. if your boat pulls to Starboard , twist the trim tab out a tad to starboard so that the water flow hitting it forces the engine back towards port . A little bit of trial and error is needed and any adjustments required are normally surprisingly small . This measure is also very useful on larger ( 30 to 40 hp ) hand steered tiller engines to remove the pull on the helm at high speeds .
Best wishes ,