3 for me
I have 3 DIY tree straps: 3' 4' and 6' with a two inch loop on each end. Normally here in the Northeast I'll travel with the 3 and 4. If I suspect bigger trees I'll go with the 4 and 6. If I know they'll be even bigger trees or am not concerned with weight, like when I'm paddling I'll take all three which will give me a 6 and 7.