ORIGINAL: Mr.Extra 260
The plane is already tail heavy. Would it hurt to put in a supertigre .60?
Right - and a tailheavy plane is not as likely to fly well in the situation you are seeing - very pitch sensitive, and will baloon on you badly on final approach. Moving CG forward helps fix that.
Think of your plane having a "balance point" right in the middle of the manufacturer's suggested range. That point should never move in your mind. CG can move, but the balance point shouldn't. Moving the CG forward of that balance point by adding nose weight (either with a bigger engine, adding weight , or moving your batteries as far forward as possible, etc...) will help balance the plane. Since you say you need nose weight anyway, then a bigger engine can't hurt - if you're going to add weight, why not add power as well?
I can't say anything about the Supertigre 60 - never flown one, never worked on one. Don't think I've ever seen one in person. Matte rof fact, I dodn't even know they made a 60 - all I see listed on Tower's site are 61's - either in a ringed or ABC version - prices are cheap, and that should be the first warning sign. The next issue I would have is that of all the engines that have been suggested, including the Saito 91 and 100, the Supertigre 61 is the heaviest(by 6-8 ounces), and it doesn't really have a very high Horsepower spec either.