The way my rescue kit works is that it is one of those Trident or similar that come with everything in a small velcro closure net bag. Since I already carry the spool and sausage on my right side, in the left side I carry the rescue kit. I cut the mirror down to fit into the pocket. I eliminated the plastic sausage. I have a tiny LED flasher for a strobe and I put these items including a small lanyard tucked and folded into the net bag. I clip the lanyard into the pocket and tuck the extra lanyard (cave line) into the net pouch. That way, when, if ever, I need it, I reach into the XS pocket, grab the net pouch and pull it out, the cave line lanyard will automatically pull out of the net pouch, if you follow. Then I can deploy the mirror, dye pouch or LED strobe flasher as required. I also have a tether line to hook me to my wife (the cave line lanyard) so we cannot float apart. It is a very small kit, so yes it fits into the XS weight pouch.
On the right side, my spool goes into the pouch with the double ender clipped onto it. The sausage clipped to the double ender does hang out but since the entire outfit is tucked way back under the wing and plate, it does not get in the way. I think my sausage is a 6 footer size, it has a velcro bottom closure.
I used to carry a UK LED light on my right upper harness clipped into the D ring and secured with tube bands (inner tube) but after having about two dozen of those flood I have given up on them - FOREVER- and have yet to find a suitable substitute.
Useful pockets on a standard Hog harness are a challenge, especially for us smaller people.
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