I wouldn't use a vacuum style sealer as this would start distilling the whisky. Vacuum distillation has been used for many years all over the world instead of heat distillation. Wm Grant's has a still at their grain distillery that uses vacuum distillation. I would also not use a noble gas as the barrier as no-one, to my knowledge, has tested the interaction with these gasses and whisky and how they may affect flavour.
Unless you intend to keep the bottle opened for 5/10+ years I wouldn't bother just make sure the cork is tight in the neck of the bottle.
Check the colour of the whisky in the Crown flask, if it looks dark then it's been contaminated with iron from the steel, as to taste I would reckon there will be a "metallic" flavour to the whisky. Flasks are designed to hold whisky for 1 or 2 days rather than weeks or months let alone years.
Last edited by blenderm; 06-23-2011 at 10:23 AM.