Wow, that's looking great. I'm just about at the same place you are in my body work. You are lucky though, I ended up having to replace the top cowl because the hood mounting area had been bubbified beyond repair. I also replaced my dash and firewall at the same time due to other large holes cut in for radios and who knows what else. I just hope it all came back together "close" enough.
I'm about to prime the bottom tomorrow, do you plan on just priming the bottom, finishing the top filler work and priming, then go back and final paint the bottom before the top? That's been my plan but I'm not sure if it will turn into a nightmare or not yet. :-/