I used the hatch offsets in the book and this is where I put them.

Front hatch 49" from bow. Rear hatch 127" from bow (about 8" aft of the cockpit opening.)

Your decision may be affected by what type of bulkhead you are using. I wanted maximum area for storage, so I moved them as close to the cockpit as I thought I could. I took the hull out to the front yard and sat in it to mark where I thought my feet would/should be. At that time I really did not give much though to what material I was going to make the bulkhead out of. I ended up using 3" minicell which took a couple of inches of footroom away from me.(I am 6'2" so the hatch is pretty far forward already due to my long legs.)

If I had to do it again I would have moved the forward hatch 2" closer to the bow and the aft hatch 2" further aft. It is going to be fine the way it is.

Jay