First I calibrate the 20D at Canon. It takes them 4 weeks to the job. But the result is 100%.
Then I test 3x 70-200 4L. All three where with backfocus. Then I test a Sigma 20-700 2,8. This one has frontfocus problems and focusing was not stable. And is very havy (1,4 kg).
Afther a short test I love the 200 2,8 L. Its realy a nice lens for the 20D. And is very sharp at 2,8 and further.