The cleanest way is to have them pre-made, my friend makes them for 25 bucks a set, but he won't be back from vacation for 10 days or so.
I personally used a 1/4 ply spacer as reccomended by Tom on my first Wild Hare, and it sincerley worked fine.
On my replacement I used the pre-made, and love them, as well.
personal preference.