Blocking Off Coolant Bypass On Sbf?

Hey Guys,
As usual, I'm gonna ask an unusual, lengthy question. A friend/associate/customer swears that one way to increase cooling "efficiency" on an SBF is to block off the coolant bypass hose from the intake to the water pump. His theory and claim centers around the fact that the bypass hose is a little less than about 20% of the size of the upper radiator hose and that it means that about 20% of the hot water just behind the thermostat gets simply mixed with the cooled water from the lower radiator hose and re-circulated through the engine, thus reducing/slowing down the rate of cooling. By blocking/capping off the bypass hose, it forces ALL coolant coming out of the intake to go to/through the radiator to be cooled. In my mind's eye, this seems to not be too much of a problem in hot weather/running conditions, but could cause issues when temps are cold. It seems that the purpose of the bypass is to mix the heated coolant with the radiator cooled coolant to help keep a more even and constant engine temp. It would seem that in cold weather, with the bypass blocked, the coolant in the engine and the engine itself could be quite hot for a while and then when the thermostat opens, you get a blast of fairly cold coolant into the hot engine. This does not seem like a good thing and appears that it could cause a shock to the block/heads and possibly contribute to warpage, cracking and/or blown head gaskets. Have any of you folks heard of this block off procedure and, if so, can you offer some thoughts and opinions? I realize that the bypass is there for a reason, but so are many other systems and features that we routinely modify and/or delete in the interest of performance. Just looking for some information/ammunition to settle a heated debate.
Thanks,
Gene

Sharad,
You say that your engine builder said:
"However, when he saw that I had plugged the water ports in the lower intake manifold (near the firewall, inline with the intake bolts) he said I needed to unplug them and run a coolant crossover tube between them in order to equalize coolant flow & temperature between the left and right banks."
That's kind of odd, as most after market intakes, for carbs, have no rear coolant crossover passage.
Thanks For Replying,
Gene

My 68 with A/C has a vacuum controlled shutoff in the heater hose. I thought they all did, but that some were part of/installed in the heater box. Your point is well taken, though. when you take the heater loop into consideration, that makes nearly 40% of the coolant not going through the radiator.
Gene