I suggest getting with someone who knows the 109's a little better then me (agent or any of the muppets/other people come to mind) so that they can help you.
For me, (and I fly the g2 whenever I take a break from the 38) in the g2 (or any plane) I try to not let people get close in on my six, as in 600/400 or closer. If someone is coming in on my six from say 1k out, I'll start a gentle turn into them, and then at about 600 (or when I sense they're about to fire) I'll pull up and barrel roll onto they're six for the reverse. If the E states are somewhat similar, I can usually get a decent shot off.
If someone is on your six say 600 out, it's going to be a bit different. Your always going to be in control in this situation in the sense that you decide where the fight is going to go. The person on your six has to follow you if they want to shoot you down. So, you decide where the fight is going, and the other guy has to react to you, meaning you'll have a "time" advantage over them. If the E states are about the same in our little example, I would start a scissors. I'd open the throttle with WEP, and roll left and flat turn, and then back of throttle as I roll back right. I might add a bit of vertical when reversing back, but not necessarily. Most likely they'll go for the shot, and if they miss they're going to over shoot, which then hopefully you can use to covert to the offensive. Obviously this all depends on the situation. If I had alt, I might try a diving turn and then try to reverse back into them.
donkey