I appreciate the replies. So vertical versus horizontal doesn't really matter as long as your diligent about getting all of the bigger air bubbles out, and presuming you can get the system up to pressure?
Sorry if this has already been asked but I have a general question about where to position the radiators and decided to ask the experts. What are your opinions about having a radiator mounted vertically with the nozzles at the top versus having the radiator laying flat?
My current setup:
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