Wow. The 600 mm is a beast of the lens. Did you purchase the old or newer version with fluorite elements. I almost purchased the 600 mm lens in addition to the 500 mm lens, but the extra weight and diameter of the 600 mm lens made it challenging to hand hold. Hand holding the new 500 mm lens which weighs only 6.8 lbs is very straight forward and easy to do.
Best,
John