With a narrow flame, continue to work the glass letting it thicken up to decrease the inner diameter. Do not try to match the inner diameter. In fact it is better if you leave the area of the seal somewhat larger in diameter than the rest of the inner diameter. If you get a constriction on the bore, it probably means you either had a too wide flame shape and/or were stretching the seal as you worked. It is very very difficult to repair a constriction.
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