Thanks for the comments. The jacket (and most 42L jackets) covers my rear, but appears to be a bit short to my eye. Another sales man used a tape measure and determined I need a longer jacket. This will not be found off the rack I fear. I do have long arms. I thought this particular jacket's sleeves were the correct length. They stopped right at the change from my thumb to my wrist.
Brooks Brothers offers suits in 42XL. They also have 41L but I do not think they have 41XL.