Hi,
Interesting idea from David to determine the length by the electrical delay.

In my lab I make my own cables. I have two favourite lengths, 2ft (60cm) and 4ft (120cm). But this is to suit my bench. I use the short cables for equipment on the bench. The longer cables are for equipment on the shelves above the bench or equipment on my scope cart.
There two kind of RG58 cable. You want the kind with a stranded center conductor for test leads.
I mark the ends with colored heatshrink tubing or colored strain reliefs.
Regards,
Jay_Diddy_B