In another post I mentioned that the Union does not get the starting '61 generals in DC present in the April campaign when starting a July campaign. Gray Lensman quickly came to the rescue with a fixit mod that you can find on the original post here
I've noticed another oddity, and that is that the Union has a huge blockade fleet in April '61, and barely anything in July. This is a fairly tremendous difference, as in July there are only about two or three blockade squadrons in port (none in the blockade boxes) vs. the 6+ present in the boxes in April. These forces (whole squadrons mind, not just ships) are nowhere to be found in July.
Anyone notice anything else? I didn't realize how much harder July was because of all the dodgy things (like units that are locked for a few turns in July, are activated well before that period in an April campaign) that occur that don't make much sense when compared with April's start.