I would just compress the cork in your floor corker for about 5 minutes, then take it out quickly put it in the Jeroboam. Use a rubber pallet to tap it in if you need too. That has worked for me in the past.
Where did you get the cage and wire for it?
Brewing since 1989 - BJCP National Rank
Fermenting: McChouffe clone, Samiclaus clone
Conditioning: Belgian Tripel, Barrel Aged Baltic Porter - in sherry barrel, Belgain Easter Ale
On tap: CAP, Dortmunder Export, IIPA, Dubbel Chocolate Stout, Wee Heavy, Whiskey barrel aged Wee Heavy, Baltic Porter