drill holes in t-stat?

lots of overheating issues/questions these days, so heres one more.
hottest day of the year yesterday, 101f, cruising at noon down the freeway, engine running around 210-220 (2/3 to H on gage)for 15 minutes or so. later, when the outside temps went down, the car ran perfectly cool. this is a recently rebuilt slant 6, new water pump, flushed radiator, used t-stat (the new one i got didn't fit well, so i saved a trip to the parts store.) stock 4 blade fan. also, no fan shroud.
anyway, a friend told me about 'an old-timers trick' to drill holes in the t-stat to allow more coolant to flow through. anyone ever try this? seems like a good idea.