Play the 3 in center and right. You would give up 10 percent more X-chart hits with the 4 in center. Furthermore, as you noted in your post, it's best to have your best arm in center.
Here's how I came up with the 10 percent more hits with a 4 in center:
CF 3 has 3 chances in 216 of coming up with 6 chances in 20 of giving up a hit: 3 x 6 = 18
RF 3 has 2 chances in 216 of coming up with 6 chances in 20 of giving up a hit: 2 X 6 = 12
18 + 12 = 30 relative chances of giving up a hit
CF 4 has 3 chances in 216 of coming up with 11 chances in 20 of giving up a hit: 3 x 11 = 33
RF 1 has 2 chances in 216 of coming up with 0 chances in 20 of giving up a hit: 2 X 0 = 0
33 + 0 = 33 relative chances
Reference:
https://img.photobucket.com/albums/v496 ... errors.jpg