That beer looks great!
I have a similar attempt in work right now, about to transfer to secondary. I didn't build a device to dump the hops. I picked up one of these pill holders at the drugstore. It has 28 little compartments with a flip top on each compartment. I weighed out the hop additions on a gram scale ahead of time and stuffed each addition into one of the compartments. I then labled each compartment with the appropriate boil time. I was jumping up and down every 2.5 minutes to dump the hop ration, so at least I didn't get bored during the boil. My brew was a partial extract as well, but all of the LME went in at the end, so the boil gravity should have been low. (Copied from the White Labs San Diego IPA recipe) I had read how the wort gravity effected hop uptake during boil, but had not found a reference to how the wort volume effects it. Can someone point me to a source on that? I am pretty new to this as well.
Primary: , Boddington's Clone, Mirror Pond w/Marris Otter
Bottled: Fullers ESB Clone
Kegged: Mirror Pond Clone
Drinking: BM's Kona Fire Rock, Dead Guy Clone, Alaskan Amber Alt Clone, Firestone DBA Clone, Magnum/Crystal IPA
Next up: Burton IPA