The manual for both the fours and sixes notes that the oil level is correct at the upper mark on the dipstick (mark "A") when the cap is fully screwed in. As the side case filler locations are all at a similar design height, and the 500 cases go on a 350 and vice versa they should be all the same
That said, that's a pain to do quickly and if you look at the top and bottom mark, they are about the thread distance apart, so there you go! Instead use the lower mark that way.
As long as it's not hugely overfilled, you shouldn't have a problem.