pokerJAH;341903 wroteIts not a free card for me realistically. If a non-spade came on the turn, I am likely betting pot. If someone slow played a better flush, well played.
You fear the Ks and As drawing to a better flush so in a sense you are looking for a non spade - seeing that free on turn improves your hand.
going to the turn for free also conceals the strength of your hand and I think you are certain to get paid off if turn misses another spade.
upon further review of the hand I think optimal choice is checking looking to reraise all in. If checks around, your hand can improve with a non spade or you can get away cheap if a 4th spade turns.
Why pot size on turn but not on the flop?