Today I changed out 7 Grundfos circs that were mounted horizontally with the motors all downward. They are 12 years old in a completely radiant home. The easy part is changing the circs, however the not so fun part is unsweating 14 flanges that had to be turned 90 degrees. FYI, IF anyone looks at the install sheet, the circ orientation is pictured. It is a very common mistake, especially if a supply house tell you they are multi-positional mounting. The check valves frequently can be omitted with cirs that have IFC valves. ......isolation flanges and/or purge ports on the return lines.
You absolutely cannot add too may shut off valves, drain ports and in your air scoop , go get the $7.00 1/8" mini shut off for the vent. You will appreciate the lack of draining the pressure of the system to change it. Also the pressure tank under the scoop....get the proper 1/2" shutoff and drain/purge valve so you can safely and quickly drain a failed tank and replace it with getting burned, steamed, or having to shut down anything. The 'check valves are addressed. No harm, no foul, just observations, not criticism. If you have time to redo the circ position, perhaps you might want to add shut off flanges and for the returns, shut-off with the purge port. That way you can 'power vent' EACH loop separately, and no air bleeding will be required!
If someone tells you that won't work, grab a large, heavy object and commence beating so sense into him. 20 minutes should do it, but if they are stubborn, perhaps get a couple friends to stop by and help out.