Too slack...you should maybe have an inch of droop under the tongue max...another way to get it right is to take them off, and the turn the tow vehicle into a tight turn to the right, and now clip the LEFT chain on so that it has minimal slack..now turn the trailer left, and set the RIGHT chain. Mark them with sharpies or a peice of red pre-flight check tape (

) and you are all set.
I have to confess its amusing to see a C130 pilot post he is concerned about trailering....

- all comes down to the comfort of the familiar I guess!!
If you have greased your bearings in September, the 'boat sitting' wont be relevant - the wheels will be fine. Check those tire pressures right before you leave of course and bring your own compressor and gauge. Pay up your 10 USD and join Trailer Boat US too!!
On carabiners - disclaimer, I am not an Mech Eng, so you should confirm the below before risking life and limb.
A 2 inch SS carabiner from We$t Marine list a Max Working load of only 66 pounds, which probably means a failure load of something like 600 pounds. My uneducated guess is the shock load of a trailer chain from a disconnected trailer will exceed this, especially if the hitch hits the ground and digs in at all.
A 1/4 inch shackle from WM is 4 USD and has a safe working load of 1000# which means a failure load of 6000# - thats more like it.
I think that is a strong case for not using carabiners on tow vehicles chains....you might be equivalently attaching your chains with string.
In an old age moment, I have a feeling I went through this discussion with myself some years ago.