opinions needed on this idea

The statement "water flows too fast thru the radiator to have time to cool" is commonly spread among hot-rodders. It has no basis in science (my M.S. thesis was in heat transfer). An engineer at Stewart ran across this and was so amused that he ran down the source (Stewart Components). The idea came from vintage cars (1920-20's) where a weak radiator cap spring would burp fluid due to increased flow pressure of a tuner water pump. A restrictor fixed that, but the guys mis-understood why.

As mentioned, you can buy an IR gun at Harbor Freight for $25 on sale. Mine works amazingly well against a mercury thermometer when checking T-stats in a pot of hot water. Running w/o T-stat wouldn't prevent over-heating unless it gives too much restriction in the "full-open" position (unlikely). It will over-cool the engine in the winter. Don't buy a "fail-safe" T-stat since they permanently lock open if you ever over-heat.