Aluminum hill repair : need fastener ideas

[Woodstock60]

I am repairing broken ribs on 16 ft. Sylvan aluminum boat. I am using stainless steel screws and am looking for ideas on how to keep the screws from touching the aluminum and causing huge corrosion holes. Thanks in advance

 

[Woodonglass]

this might be informative...https://www.bassresource.com/bass-fishing-forums/topic/20093-what-screws-bolts-for-aluminum-boats/