Why would you want to drill a hole in your thermostat? Surely that will just cause you more headaches down the road. You want your engine to warm up to operating temperature as quickly as possible, because when it is cold (or really hot) is when you get the most wear+tear on your engine.I remember on my e36 after doing the thermostat it immediately shot up into the red when I started driving. In my case I also had air in the system, but just jacking up the front end and loosening the bleed screw on the top of the radiator, then starting the car and running with the heater on seemed to get rid of all the air. I am not familiar enough with your set-up yet, but I imagine the process should be pretty similar.
It could just be that your gauge is not calibrated right. If you know anyone with a temperature gun you could check your hose temperatures to get an idea of your operating temp when your gauge shows 3/4.
And I can't recall now, but isn't the top hose the return hose (gets hot first), and the bottom hose is the feed hose (stays cold longer)? If that is the case the top hose should get warm when your thermostat opens up, and the bottom hose should get warm a short while later, after all of the fluid has circulated through the radiator. Though maybe I have the flow direction backwards.
On some thermostat's, they come with pre-drilled holes to help elevate the air pockets that get stuck, making bleeding the system a helluvah lot easier. This hole is tiny, but helps fluid and air get by if need be.
My set up (S52 with M20 late model radiator, late model coolant res) doesn't have a bleeder screw...but I may just add one now....We will see.
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