Let me start by thanking you for looking at my question.
My oil burner has a 3/4 inch line from the circulator to the heating pipes that feed the downstairs. The 3/4 line splits into Zone A and Zone B which drops to 1/2. During a reno this summer, zone B was cut and capped as a project to come back to. Since the temp outside is near freezing now is as good a time as any.
Should I run the currently capped pipe back to where the junction was and do a 1/2 x 1/2 x 3/4 inch T (Idea B) or can I run the 1/2 inch into the 3/4 and because its reduced later down the line I'll have enough pressure to still feed Zone B (Idea A). Picture attached because I dont think I am explaining myself well. 