Hi,
I feel that a stat is a very good idea, to insure engine oil reaches a proper operating temp to provide best possible lubrication *and* to boil off water vapor and other crankcase contaminants properly *and* to keep the oil cooler from possibly being subjected to higher pressures at startup with cold oil.
Yes, it's one more thing to go wrong, but a pretty well-proven system. Simplicity is why Revington offers a passive cooler (a modified oil sump with a couple air tubes passing through it), but that also requires some cutting and welding of the frame to route air properly and has no easy means of controlling the cooling effect.
Rick's method of covering the cooler will certainly work too, but you do have to pay close attention and an oil temp gauge might be a handy accessory.
Relatively new are the Mocal (maybe others) 180F oil thermostats that are combined with the sandwich/take-off plate. These take up no additional space to speak of (slightly thicker), simply use one in place of the traditional take-off sandwich plate. If interested, see part SP1T at
www.racerpartswholesale.com
Using this means 4 fewer connections in the oil lines, each of which represents a possible leak or loose fitting, not to mention the cost of large AN fittings if that's what's being used, and no separately mounted thermostat to mount somewhere in the engine compartment. A spin-on oil filter adapter will be needed first, with this take-off/thermostat on top of that. And, adapter fittings are needed for whatever type of lines you are using to route the oil.
I've got one installed on my TR4 with AN10 hoses. Photos of the installation are at the link below, by my signature, if you want to take a look. If I had it to do over again, I'd probably use Earl's Pro-Lite 350 nylon braided hose, instead of stainless braided. It's lighter and less abrassive to anything the hose rubs (I ended up wrapping the S/S hose with plastic wire wrap).
Cheers!