How clase can I put inwall to a plasma diaplay? I'm short on space so I would like to mount the font channels inwall 4-6 in from the display. Is this going to cause any issues?

If the speakers are shielded you won't have a problem.

In wall speaker are not recommended for optimal audio. If you have WAF issues, then I can understand. You also want the left, right, and center speaker drivers all at the same level which is ear level when sitting down. Display distance really is not a factor unless it is so far away you the sound is disjointed from the picture. Speaker positioning is more reliant on their prespective distances from the side walls, floor and ceiling. Too close to any wall and bass frequencies can muddy the overall sound and that should be your primary concern.