If you're flying the Tiger 60 as a "second plane", one step up from a trainer, sport-flying with the occasional loop and roll, then that's the kind of flying model companies base their engine recommendations on. However, the Tiger 60 is more than capable of flying serious aerobatics, with lots of vertical components, and for this kind of flying more power is pretty much a necessity.

If you're inclined to go four-stroke, a Saito 72 will be great for sport flying, but a Saito 100 would be in order for the aerobatic stuff. Keep in mind that aerobatics are best flown with constant throttle management, and wide open throttle only on vertical manuever segments. Other than that, as the man says, a bigger engine cruising at reduced throttle will make less noise, burn less fuel, and be kinder to your airframe than a smaller engine at full throttle.

If you want to consider two-stroke power, it's almost a waste of money to buy a 60 size engine these days, because something like the Magnum 91 XLS weighs the same and mounts the same as a 60, but with significantly more power. Same deal with the throttle--cruise at 2/3 throttle, use full throttle to punch up some altitude. It really is marvelous to pull up into a big square loop or a big diamond loop in a Tiger with 90 size two-stroke and not have to feel your engine straining. This is not over-powered, this is simply adequate to power-gobbling maneuvers.

Whatever engine the model will carry without getting over 25 oz/sq in of wing area (for a "60 size" model), more power is always better. Thrust of 1-1/2 to 2 times the model weight is the norm for aerobatic flying. Pulling an 8 lb model straight up with the inevitable drag adding at least a few more pounds of weight equivalent, 12 pounds of thrust is about enough, 15 pounds certainly not too much.