It's doable though. I've actually gone as high as four in an attempt to get a rush off of oxycodone.
In retrospect it would have been a lot smarter to have just used a larger rig. I had larger luer locks for use with filtering larger volumes of solutions but didn't have the right sized tips. Considering the limited solubility of oxycodone (approximately 150mg/mL IIRC?

) we prepped up four 1mL insulin syringes with six blues (30mg oxycodone tablets) per rig. I had my friends hit me with them as close to simultaneously as possible. Still no rush but it's definitely possible to use multiple needles at the same time. It might be a bit crazy as you said though.
It beat the hell out of the 8 IV lines I ended up having to have in the last time I was in the hospital when the dumb fucks had to pull the PICC line that they managed to contaminate.

I digress though. Other posters have mentioned the issues surrounding injection of this particular preparation of methadone so I won't get into that. I myself have used IV extensively but never developed a needle fixation. To me it was just another ROA no different from any other. However; I've known plenty of people that have had said needle fixation. As another poster mentioned perhaps you could just shoot water?
Considering how little there is to gain from shooting methadone due to it's inherent properties (lack of rush, large volume of distribution, etc.) you may be better off taking the methadone orally & just injecting water to get the needle fix. The end result would be the same with less harm involved.
You can get high off the methadone, get your needle fix & not risk harm to yourself from injecting something that provides a negligible benefit to inject.