i wouldn't worry about the strength of the plug. it is only really used when you load the bearings. once that is done and the stem bolts are tightened, you could undo the top cap and plug without harm. the expansion force is not that great that the integrity of the steerer requires it to avoid getting crushed.
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coasting, few quotes are worthy of him, and of those, even fewer printable in a family forum......quote 3alarmer
No @coasting, you should stay 100% as you are right now, don't change a thing....quote Heathpack