One other thing to consider is how much weight you're going to put up front and how the bike will handle it. If your bike has track geometry beyond the pursuit bars, weight up front might do bad things to the handling. You can get some rough idea of what might happen by strapping/tying some weight onto the front of your handlebars. Tie/prop it up as best you can to approximate the position a handlebar bag would be in, and ride up and down the street a few times. (If you can tie it up securely enough, try riding down a hill with it, too) You can estimate the weight of whatever bag(s) you're considering, added to the estimated weight of the contents.
Depending on the results, you might find you're better off putting the weight in back and using only a small map case and small top tube box/bag/handlebar roll/whatever up front for small things you want access to while riding.
If I'm making faulty assumptions that you've got track geometry along with your pursuit bars, feel free to disregard the above.
FWIW, I'm also a long distance fixie rider (and I'm the maker of Dill Pickle bags, in interests of full disclosure). Good luck!