Hi, I am wondering if there is a Y shaped flank cinch, just flat leather to use on my saddle with double C rigging…I am not happy with just the tongue of the buckle into the latigo strap…and if I do the knot at the top it makes a bump under my leg…Can’t seem to find info on how to use the feature of this rigging without just using the buckle…or am I worrying about something that I don’t need to? Thx for your input.
No such thing and it’s not how it’s supposed to be used, anyway 
Here is a standard wool girth with a normal buckle on both ends.
https://stagecoachwest.com/catalog/mohair-cinches-p-3687.html?osCsid=cjgvpqo1bkkrv8kt3585hpfvl5
Use a good quality leather latigo and cinch that sucker up, buckle it, and go
You can use the double C to create a different rigging position, but no, you are (IMO) worrying about nothing.
A GOOD buckle and a GOOD latigo matter. I’ve seen stiff, hard nylon latigos I just didn’t trust at all, they feel dead. And I use just this simple old school wool girth on my main horse and we ride in some crazy crap. and no, I don’t like that knot under my knee so I buckle and go.
THey do sell these converters but IMO that’s just more stuff to break.
https://stagecoachwest.com/catalog/western-converter-p-264.html
