i been thinking of planting 3 oak sapplins in a pot, so i could get the roots closer togather, then when they got healthy and well rooted to braid them, as they growed,
well maybe not oak becuse its so slow growing,
but you get the idea,
good potting soil and jobe spikes and weeding should have it root bound in one season if the thing is in a gallon pot or coffee can.. then transplant to a well drained spot.
dont know if trees work the same as inside ivy vines, bit i give my ivys a cup oc black cold coffee once a week, and a jobe spike once a month, with this continued over the summer the ivy will take over the room, so dumping coffee grounds might make the same effect on a strangling vine on a sapplin.
in the louisiana woods, we got a hard growth, olive green vine here that is hard as bamboo,(we call it trip vine)
if you gould find some of that and start it next to an early sapplin bout pencil size and tightly wrap the sapplin it should strangle the sapplin tree as it all expands, and impress a good spirial into the tree,
hummm,
bing!

thinking on this i got some really heavy copper wire i have, i took off of a replacment telephone pole. i used when i made my pole barn, with that inside a old cheep section of garden hose i should be able to bend or strangle one of them caltoba or sycamores that took over my garden.
i cant phisically garden anymore so ill raise walking sticks...
or at least experiment...