We have seen how easily the Heat have been able to get to the rim when KG leaves the games. I don't want KG wasting a ton of energy on defense trying to stay with Bosh on the perimeter and also trying to get back to help underneath.
Bass is more than athletic and strong enough to stay with Bosh. Yes Bosh has a 2 inch height advantage , but as long as Bass is keeping him out of the paint and contests the mid range jumper we should be fine.
We need KG down low on D to stop Lebron and Wade from driving and need him to be fresh enough on the offensive end to give us 20+points if we are going to win this game.
As you said, he's giving about two inches to Bosh and for someone who is making most of his offense through outside shooting rather than post play, height is a more important aspect to disrupt his rhythm, not muscular strength.
The last thing I'd like to see is Bosh giving sort of a big boost to the Heat with his jumper. Keep KG on him. He's definitely not a very good one-on-one defender, let alone be a good weak-side helper. So, by keeping KG on him, you may exploit his physical weakness leftover from the injury to the full extent.
While I'm not buying that Bosh is going to hurt Miami, I don't think he's the key player even at his best. There is only one player for the Heat to get in a zone that will mean trouble for your team, get the crowd involved and totally motivate that team, and it's not LeBron James. It's Dwyane Wade. You can see that even at his teammates' faces. Take Wade out of his rhythm and let James be the leader. That's how that team will collapse.