Hey I am just a old guy playing with trees for fun as a hobby, so take this for what its worth... It seems like instead of making your cross at the splice and then taking out the slack at the knot, you could make the cross at either the portawrap or the intersection of the rope to portawrap and when you pulled it tight the rope would cross mid splice without always having to readjust the knot?
doubled over length of 3/4" double braid nylon with porti centred in the aforementioned then with a running bowline or stilson or sometimes a running clove to secure on the tree.
dontt use a dead eye much at all prefer a long length of rope to move the load and wear any where on the rope. Retiring worn out eyes is got old. no time for splicing and not about to pay for something that is the equivalent to a doubled over piece of rope. same for mounting a block or oolds or ring n ring.
also really like using 20' pc of rope with a wrap 3 pull 1 finish with a double overhand knot and another overhand knot backup or my Proknot.
never had it jam up to the point it can't be undone
have used what you show many times easy peasy lemon squezy
I’ve made cow hitches hold the porty straight up. That way is way more appropriate on a 6 or 7 foot base. But if your being a perfectionist and you have a large enough sling, you can stiffen up that device way more. I get what your trying to say because the bowline isn’t “issued” to this application. But add a Yosemite tie off and that set up will accomplish the task all the same. What gets neglected is redressing the ground mounted friction device after it is extremely loaded