I have heard some people use mid board leash points. Wondering if I should put some in the board I am building. Any info from people that have used them would be appreciated.

Fine in flat water.
Catastrophic in real surf.

If you are going into the surf, consider adding two leash attachment points.

II would put one ahead of the standing area and also one at the rear like most boards.. Leash plugs are cheap.

I attach a booger leash to the handle for flatwater paddling, but as the others said go the tail plug when surfing of heavy downinding.

Thanks everyone. I am going to put one forward and probably 2 in the tail. As Davidjohn said they are cheap. Just have to put the reinforcement in the right spots. It's a hollow board.

Hard shell boards need a bungee type leash to soften the shock of the leashes sudden pull on the shell. Just a short 6" length is enough, but either doubled up or bigger diameter than the leash. A urethane leash still transmits shock loading, even a 12' leash, that can stress fracture a hard shell vehicle.

Definitely use two leash plugs at the rear, whether or not you put one up front.

Using double plugs like on a big wave gun means that, when you use two leash cords too (which you MUST do, not use one cord run through both) the leash will stay more centered on the deck, less likely to drag in the water. Which is handy, quite apart from the extra security of two plugs.

Thanks I plan to put 2 in the tail and 1 fwd of standing area. They will be inserted into blocks of high density foam inside the board. Next to a rib so nice and strong.
I have been contemplating drilling a hole and passing a Dynema loop through. With a backing plate inside.

If I drill a hole and pass this up through it with loads of epoxy. Would it be stronger than a plug?

As you know, cured epoxy is brittle, and cracks with minor impact.
A slurry of chopped glass mixed with epoxy, slowly with few air bubbles, is strong.
Reinforce with glass, at least 14" radiating from the leash mount. Triple layer 3" dia. 2 layer to 6", a single layer for the perimeter. That is minimal.