The Goldberg Tiger 60 often comes out a bit tail heavy as it has a longer-than-normal fuselage for a sport plane. Picking an engine on the heavy side will usually benefit the Tiger 60.

An engine like the .65 LA has several benefits. The air bleed carburetor is less sensitive than a twin needle type and rarely requires retuning. The plain bearing design isn't subject to problems with rust; the engine won't require after-run oil and would be a great choice if the plain will be flown on floats in the future. The primary downside of this kind of design is that plain bearing engines are more sensitive to lubrication types used in the fuel mixture. They generally don't run as well on synthetic lubrication and will produce more power, run cooler, and run more smoothly when significant amounts of castor oil is used in the fuel mixture.

An engine like the .61 FX also has several benefits. Dual ball bearings make the engine more flexible with regard to fuel blends; synthetic lubricants generally won't degrade the performance or longevity of a ball bearing engine. A twin needle carburetor can be easier to fine tune than an air bleed carburetor.

The notion that engines with twin needle carburetors and dual ball bearings are always better or more powerful than engines with air bleed carburetors and/or plain bearings is simply not true. Every cheap Chinese engine of dubious quality is twin needle and dual ball bearing (Aviastar, GMS, Evolution, etc.), while only the finest engine manufacturers offer models with plain bearings and/or air bleed carburetors (O.S. Max, Thunder Tiger, Enya, K&B).

To be more specific, the .61 FX doesn't outperform the .65 LA; the .65 LA will out-turn the .61 FX on a number of different props using the same fuel and glow plug. The plastic backplate used to lighten the O.S. Max LA series engines lowers their maximum compression and contributes to their reputation for weak performance. The .61 FX is an older design, and isn't a particularly strong performer with the stock muffler, either.

At the end of the day, your Tiger .60 will benefit most from the .61 FX for two reasons:

1) The .61 FX weighs significantly more than the .65 LA, and will help balance the Tiger .60 better

2) Fuel with 50% or more castor oil lubrication is very hard to come by these days. You'll most likely be flying with fuel that's 80% or more synthetic oil for lubrication

If an O.S. Max 2-stroke of .61 ~ .65 displacement is the limit of your shopping choices, then buy the .61 FX. If spending the extra money to go from the .65 LA to the .61 FX makes sense to you, spending a few extra dollars to jump from the .61 FX to the .75 AX is also a no-brainer due to greater performance and resale value.

You would also find the Super Tigre .61 ringed or .61 ABC, the Super Tigre .75 ringed, the Thunder Tiger Pro .61, or the Magnum XLS .61 to be very good matches for the Tiger .60 airframe. They may not offer the resale value of the O.S. Max .61 FX, but they offer better performance for $70 to $90 less.

Good luck and good shopping!