is this driveshaft sitting exactly where its suppose to?

Sorry for the bad picture, but this is with the driveshaft attached to the rear yoke, and the picture is how much the yoke is pulled out from the transmission. It reads pretty much exactly an inch. The thing that I question is that is reading it from the rubber seal. If I don't include the seal it's more like an inch and a half. Should I have it shortened a 1/2 inch, or good right where it's at?
Also this is a slant six driveshaft. Is there a reason why the driveshaft tappers toward the rear yoke? Wouldn't it be stronger the same width all the way across?

Thanks!