peat is a totally different beast to the ussuall beechwood smoked of hoephner and weyermann, beechwood smoke is like many smallgoods in flavour and much more suited I think.
The alder wood used in the alaskan porter is also awesome, i liken that to a more sweet honey smoked smooth ham style rather than the slightly rougher general smoke you get wih many other smallgoods. Apple is said to be similar.
500g in a porter would not even be noticable really, I'd proberly start with around 15%, around 1-1.5kg and go from there. Most smoked beers with the weyermann that are after a reasonble hit of smoke would use around 50% but for your hint in a porter go 15% and work from there.