I have used 4-40 connectors on 1/4 scale Tiger Moth and 1/5 scale Albatros, without any problems. Also use the 40-50 # plastic coated SS standed fishing leader from Pro Bass. Comes with a bunch of crimp connectors. Works great and price is right. Seems like same type material in the pull pull kits that are available-(.024 dia.) I think something else will fail before the connectors or leader will break. Just my $.02.