On a XHD stand up tuna rod, should I mount a tuna block forward of the reel seat? I know the guy is going to use a reel that has a forward strap clamp and with hypalon wasn't sure if it would damage the grip over time or not.

You don't want the clamp on the grip - it's almost impossible to get it snug without completely deforming the grip and yes, it will damage the grip over time.

If the seat is mounted with the fixed hood to the rear, you may find that the forward area, the threaded section beyond the locking nut, will be sufficient to accommodate the clamp. On a uni-butt style handle, the clamp may fit just forward of the ferrule nut.

You really need to get the reel/clamp and see what's needed for the clamp to fall on something rigid. It may take a block and it may not. But it's easier to install one that goes unused rather to have to retrofit one later.

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Like Tom said, get the reel. Some older, larger reels had strap clamps on both the front and back.