40D metering

How can I check the accuracy of the meter system of my 40D.

I was taking a indoor picture with both the 20D and the 40D on App. priority mode. Seemed to get a couple of stops more on the shutter speed on the 20D. Both had an F4 lens with lens wide open.

When I stopped and put the same lens on both cameras seemed to get close and after a while they were the same.

Just concerned since 40D is new want to make sure it is right on.

Shoot outside on a bright, sunny day and see if camera follows the Sunny 16 rule.
Shoot gray card and check where the peak in histogram falls.

Just off the top of my head, there must be some other ways..

Shoot a solid colored, evenly lit wall as b/w jpg. Should be 118 on color selector probe, but anything between 113 to 123 is within tolerance.

I posted the other day that when I first took the 40d out I wasnt getting the results that I expected, shooting jsut before sunset with good light at iso 400 and wide open for example f4 or a couple of times with a different lens f2.8 I was getting shutter speeds much slower than I would have expected around 1/25 a lot of the time.
The next day I went back to same location, even took my tripod as there was a shot that I wanted, the day was more overcast and it was later in the day so the light wasnt as good, but this time the shutter speed was upto 1/300 or faster. this was what I was expecting the day before.
Still not sure what was going on but it seems ok now.