I dont use tubing or leaders of any description so i admit im having difficulty trying to visualise your probkem adds , however since i always use running set ups myself am i right in saying that by buffer bead you mean the thingy thing that stops the lead running down to the hooklink ?
Most tackle firms , i believe anyway , do complete running set ups so i would imagine that their rig tubing fits their terminal tackle ?
Ie solar rig tube =solar buffer beads .
Then again i might be talking utter rubbish .
As a sidenote , why would a club insist on tubing ? Or am i going to get that old chestnut about mainline damaging the fish's flanks ?
Just a thought but i wonder if the gardner beads might do the trick ? They have a tapered bore so providing the rig tubing was cut to a point , it MIGHT fit nicely into the bead ?