Bah! Humbug! And I'll explain why I think that. Playing guard is a lot less demanding from an athletic standpoint, speed, hip flexibility and such isn't nearly as important as for a tackle. Peat however have those skills and they will only benefit him.
The most important thing for any oline player after being big and strong (obviously, duh!) is being able to move in an efficient manner and placing your body in the best position to succeed against the defender. Understanding the concepts of each play, how you take the best angles, to position yourself. That is what he needs to learn, it will not ruin his career in any way but it might take a little while for him to adjust to it.

Really? So the whole pulling down the line, getting downfield and maintaining run alleys that's not demanding?

Or swinging underneath, or jumping ahead of a defender to trap block a big strong man, without holding him, is not athletically demanding?

Guards, Centers usually engage defenders near post-snap; whereas Tackles often read defenders and move to seal them out of an area - Peat is used to a more read, react style of play rather than pre-snap read and react upon snap...

Believe Peat's length is also giving him problems at guard where he's more naturally suited as a Tackle; so, I'm not surprised he's really impressed more at Left Tackle...

No one wants to say it, but Peat needs to be at Left Tackle if he's to maximize his potential...