Would it be safe to run high octane on a stock engine and not weld the ears?

I would run fuel with a high enough octane level to prevent your engine and present state of tune from experiencing detonation.  This applies to any cylinder, whether it is stock or highly modified.  I would run your present cylinder until the engine needs bored or a crack appears.  Then have the ears properly reinforced. Look at the cylinder before each ride.  Dirt will start to collect in the **** area.

All of the LT500 cylinders do not have the same strength in the area that has the cracking problem.  I find contamination in the aluminum in the right rear portion of the cylinders on a lot of cylinders that break.  The contamination appears to be casting sand that washed out of the runners and collected in the area of the cylinder that cracks.  This type of problem can usually be traced to poorly designed molds, soft cores, using sand that was not prepared correctly and or unskilled foundry workers.

I feel that the cylinder design was flawed.  **** cylinders are the result of the inconsistency in the quality of the casting and the poor cylinder design. 

High octane fuel will help reduce detonation on any engine that is having a detonation problem but may not eliminate it on a poorly designed or tuned engine.  There is a ton of wrong information on web sites about how much compression you can run for a given octane fuel.

I have not found a compression number or compression ratio that is a limit for premium pump gas nor have I found a compression number or compression ratio that always requires 110 octane fuel.  I think that the majority of the information that two stroke engine builders and owners are using is just folk lore borrowed from the automotive industry. 

The majority of the automotive engines will run detonation free on 87 octane fuel.  Put a turbo on one of them and add a couple psi of boost and now we need 93 octane fuel to run detonation free.  Add more boost and now we need 100 octane fuel.  Add even more boost and now we need 115 octane fuel to run detonation free.  In this example the compression ratio or the cranking pressure was not changed but the octane requirements of the fuel went up as charge density, dynamic cylinder pressure and power increased. 

This trend is also present with two strokes.  As the overall design of the engine is improved, the engines ability to increase charge density is improved. As the charge density in a two stroke is increased, the fuel octane requirements of that engine is also raised just like when the boost on a turbocharged four stroke is increased. 

Improving the design of the cylinder head on a two stroke reduces the engine's octane requirements.  Increasing the power of a given engine usually increases the engine's fuel octane requirements.  Advancing the timing, over restricting the exhaust system, and butchering the transfer ports will usually raise the engine's fuel octane requirements without out increasing the power.