He's also DEAD!
The porch scene before the hunt was great. I don't know if he was hard or not, but he definitely puts his hand in his pocket and fondles himself. Super hot! The attached screen shots don't do it justice...you need to see the video.
Here's a couple of screen captures from Fort Massacre. He's the guy on the right (although the bulge makes that rather obvious).
I've searched in vain for a shirtless pic of Forrest. The best I could find is attached, but it's not very revealing, and there's no indication of what movie it's from. I know in later years he showed some fur in his open shirt collar. Hopefully something will show up in the near future - I'll be watching.