Hello Noel.
You need 5 metres of harness to make the shoulders, belt etc. the crotch strap is a seperate affair and to be honest should be of softer webbing to avoid rubbing on your suit (and anything else
).
Even if you want to have a go at doing your own harness (which is very simple) I would recommend buying a crotch strap assembly as it is stiched to avoid unravelling at the most inopportune moment (and yes that can happen). You can get a soft strap through a smaller slot in the backplate - I've seen quite a few of these and with a bit of wriggling you ca do a good job. You can get one
here
Hope that helps
