How do you cook the BIG lobster tails from Sam's Club and not have them get a little tough like??

We've bought them from Sam's for several years now, and we love them and the price! I usually simmer them on the stove top.....watching carefully, etc., etc., but even though DH says they are perfect and he loves them slightly firm, I'm not that thrilled. Oh, they are delicious in lemon butter and all that, but I wish I could cook them a little more tender, like some of the restaurants cook theirs. Of course, what you get at a restaurant is only about 1/4 or 1/3 the size of Sam's lobster tails. I have ordered from the Lobstergram and baked them according to their instructions, but they were so small that baking them was perfect.

If you cook Sam's tails any different than boiling, I would appreciate hearing how you fix yours. TIA AnneMary