I couldn't wait for Christmas

[neuroanatomist]

With the 1D IV I have the following results;
24mm 0
35mm +4
50mm +4
70mm -1
I could discount the 24mm as it dropping off will not hurt much. The drop from 50mm to 70mm with a difference of 5 bothers me.

I'd be concerned, and sending it back makes sense. You could pick reasonable AFMA values, maybe W = +2 and T = 0 or +1, and use FoCal to run a single-AFMA aperture sharpness test at 50mm and 70mm, to see how they compare.

I have something similar with my 28-300L - it's around +4 at 28mm, 50mm, 100mm, and 300mm, but around -2 at 200mm. If I'd bought it new, I'd send it back (I bought it used for around 60% of the current new lens price, and while I like it, I'm not sure I like it enough to keep it, may swap it out for the 24-70 II, actually, or perhaps the 50L). As it is, looking over my EXIF with the lens, only around 10% of the shots are between 150-250mm, and it's f/5.6 at that point so AF errors aren't as critical as with an f/2.8 lens like yours.

[HDNitehawk]

I'd be concerned, and sending it back makes sense. You could pick reasonable AFMA values, maybe W = +2 and T = 0 or +1, and use FoCal to run a single-AFMA aperture sharpness test at 50mm and 70mm, to see how they compare.

I took your advice, to extremes. I printed off a new chart on the Pixma 9000 using matt paper. Rearranged the lights to make sure a bit and got a little better results and the range tightened a bit.

I ran the aperture sharpness test all the way across the board. This lens seems to back focus at 50mm and then it falls off at 70mm.

This is what the chart looks like. I think a person could take this lens and be very happy with it because it performs so well at 50mm.
I am still leaning toward sending it back.

This is tonights results and is the IQ at f/2.8 at each setting from the foCal aperture sharpness test;

Setting	24mm	35mm	50mm	70mm
-2	1139	1095		1101
-1	1109	1132	1150	1088
0	1139	1122	1147	1101
1	1125	1161	1151	1075
2	1130	1152	1169	1069
3	1012	1002	1189
4			1170
Average	1	1	3	-1