Does anyone have experience flying a Code 0 on a 25 foot or similar sized Hunter equipped with a B&R rig? Also, how far in front of the jib would be recommend for proper balance. Thank you.
Our First 260 does not have a B&R rig like your boat, but like your Hunter is designed to not use overlapping headsails. It's also the exact same length; 7.5 meters.
This non-overlapping rig deal is actually a very modern setup, 95% of all modern raceboats are configured like this. As you have found, the weakness of the setup is light air reaching. To do this effectively you need to add a Code 0 or Code 1 reaching sail. In apparent wind angles up to 45 degrees, it will transform the boat. Your boat even more so, as typical of Hunter B&R rigged boats it is under powered (230 sqr ft sail area).
Here we are in 8 knots of breeze, at hull speed with a apparent wind angle of about 44. It feels like you are sailing straight into the wind... however it is the boat's speed that is pushing the apparent wind so far forward, in actuality the true wind is just forward of the beam.
Its easy to use and fly. As for tack position, its less about ballance, and more about practical issues. I've written more about this sail and its use on my blog.
http://rarerarebird.blogspot.com/2014/01/260-mod-reaching-asyms.html
And some more about general spinnaker selection.
http://rarerarebird.blogspot.com/2014/01/downwind-sail-inventory.html