I felt the double was takeout but often converted to penalties, I felt I had enough shape to justify bidding the vulnerable game. Partner felt the double was just penalty.
My understanding is that it is more important to protect the possibility of our game then it was to score an extra 100 in setting a dead contract, hence that double was still takeout. To reinforce this point, I pointed out that by doubling you mark the position of the cards and it is now only down 1 for 200 instead of down 2 for 200 undoubled. Hence this double should be used for takeout with the expectation that partner will often convert with flat and even defenseless hands.
Thoughts?