Dave;
If you've never towed behind the bike, I'll offer the following.
From the pic, that looks like a good sized cooler. Normal rule for balancing a trailer is 10% of the weight should be on the hitch. Once you get it loaded, you should check how the load is balanced. If that cooler is heavy with food/drink and Ice, you may need to pack the heavier stuff towards the rear of the trailer to get it balanced so it doesn't waggle going down the road.
Looking good by the way.
