I hear that, about "too compressed" - learned that the hard way with meat loaf. There's a very fine line between tender/juicy and tough/dried out. Or, with burgers, between compact/holding together and loose/falling apart.
One time I had to make up a huge number of smallish burgers for a large party. My friend and I mixed a can of taco sauce with each 2-3 lbs (I forget which) of ground beef to kind of stretch it - and then grilled them. We had raves for years about those burgers and I loved them, too - unbelievably juicy.
What about this "grilling while frozen"? Is that a good technique for keeping it moist? I've never done that, but it sounds ideal for me and "mine" who like our good meat rare.
Grilling while frozen is how all the burger joints do it. We do too. The secret to moistness is to only press on it one time after you have turned it. Most people stand there and beat the bejeezus out of it until there's no juice left.
Another thing to try, other than taco sauce, is Lipton Onion Soup. Pour one packet per lb of chuck. Makes a super-tasty burger.