Depending on the ring size, you may end up using the second chain ring rather than the larger one. I run my ring where the second one would normally go with nothing on the outside. Using BMX stackbolts as mentioned or track bolts works fine. I used a set of washers for quite a while with a normal set of stack bolts. How long are the crank arms, by the way (should be stamped on the inside of the arm.)? You may find a longer arm (175) may be a bit dodgy for cornering.