Guys,
Had I not done my lattice work on mine, I'm betting I would've been in the same boat. surf, check out [link=http://www.rcuniverse.com/forum/Lightening_the_GP_Skybolt/m_2496934/tm.htm]this thread[/link] I started when I was building my Skybolt. I am also going with a Magnum 120 up front, and just started covering two nights ago. I managed to take 3.9 oz out of the tail, which translates into roughly a pound up front. With my RX and battery over CG, I need no added nose weight. It balances perfectly. However, I do have to add 1 oz in the right top wingtip (on CG) in order to balance the Skybolt laterally. My Magnum is inverted, and I guess I need to compensate for the off center engine, and the exhaust. I think a sideways mount would've been even worse, just on the opposite wing.

Now I just need to figure out my ground clearance...but that's another thread.