Hmmm. I thought it was a given that you should have an orifice in the bypass hose if you use a modern thermostat. That's how my TR4A is configured. I'd prefer to use the original type of thermostat, which shuts off the bypass when the car is warm, but they don't appear to be available any more except perhaps at outrageous prices. Yes, with the orifice you are theoretically bypassing some coolant while the engine is warm, but it's minimal--the orifice's restriction is way more than the radiator.
Well, maybe some have gotten away with it, but I still wouldn't try it. I think it's a risky practice for little benefit.