Magic Melvin,
I would not recommend putting the 9cc gasoline engine in. I have a Tiger 60 with a JBA 15cc gasoline engine and the two are a great match power wise. I just don't think the 9cc would be enough. I just flew my Tiger today as it is my "bread & butter" plane that I take to the field every time. The tiger 60 builds a bit tail heavy and you have to add weight no matter what and bend the mains back a little to get them behind the CG otherwise the tail drags. The JBA 15cc was a bit heavier than the 60 nitro I took out of it so I was able to remove the balancing weight I added to the nose. I think the 9cc would be a bit short on power and weight. I can just about hover vertically with the JBA and it doesn't seem over powered. The only gas engine that I know of that I would put in the Tiger would be another JBA 15 or I would try the NGH 17cc. If you get the JBA 15cc you will also need to get a DLE 20 carburetor to replace the stock one as the throat diameter is too big on the stock carburetor and it will suffer from the rich mid-range issue. I have not had any problems with my JBA 15 since I replaced the carburetor although I have heard of people having the connecting rod break. I have about 2.5 gallons through mine...I fly the stew out of it. Just trying to give you some information so you can make an informed decision. I read a thread here on RCU where one guy was putting a 20cc DLE engine in. I think that the 20 cc DLE would be too much, but I guess that all depends on your flying style.