Bit of a difficult question to answer but needs to be tight enough not to shimmy but if you have to put effort into locating the tangs, thats too tight.
Bear in mind that leather will expand and contract depending how dry or damp it is.
After a run the bonnet might be hot enough to contract the belt so it will not undo unless you damp it. it could be most embarrassing explaining to a police officer why you were peeing on your belt having needed to open your bonnet.
You may have less of a problem with a double buckle i would think as you have three joined strips of leather rather than two, and if too tight you can elongate two punch holes rather than one.
regards john k
