My pleasure!
There's no reason you can't use two strips-and-string assemblies, but that's hard to get into the bass - you really have to get the string of the second handle on the post _after you put it in the bass.
Also you have to mark the post so you can tell which way round it goes, because there's nothing to stop it rotating. Careful cutting of the end of the aluminium should fix that though.
I can't really remember who Dad and I learned it from. I think it was my cello teacher, some time in about 1969, but my memory is a bit dicey nowadays - we may have taken it to someone else.