Another alternative from using any spacers is to make a quick jig to hold the stringers in position while bedding. See my post here >> https://forums.iboats.com/threads/restoring-a-1990-larson.741569/page-2#post-5640304
I made jigs to hold and support all the bulkheads and stringers in the correct location and about 1/4" off the hull, (you can see the daylight under the stringers in the post above). Then you just tool in the PB under the stringer / bulkhead and do your fillets.
Doing it this way will save you the step of cutting the stringers to the correct height afterword's which can be cumbersome. Any way you choose will be the "right" way for you. Good Luck !
I made jigs to hold and support all the bulkheads and stringers in the correct location and about 1/4" off the hull, (you can see the daylight under the stringers in the post above). Then you just tool in the PB under the stringer / bulkhead and do your fillets.
Doing it this way will save you the step of cutting the stringers to the correct height afterword's which can be cumbersome. Any way you choose will be the "right" way for you. Good Luck !