Extending steam to addition

Scott24

I have one-pipe steam with dry returns. I am adding a 2nd floor addition on the far side of my house from the boiler. I need to serve a new first floor (40 EDR) and second floor (25 EDR) radiator that are 16 feet from existing mains, 35 feet from my boiler, on the other side of a stone foundation wall and unfortunately sitting above space that is open to the elements. My boiler and near-boiler piping seem OK for the additional load.

Option 1 (least expense and mess): Take off of closest main with a 16-foot 1.5" horizontal run-out (pitched 0.5" per foot) that has the second-floor riser take-off before getting to the first-floor riser. Add a riser vent to the second floor to try to balance the system, but no drip on the riser. (note: should I be putting the first-floor riser first on that run-out?)

Option 2 (may not fit) Take off of closest main with a new main and new dry return to serve the new radiators. If I do this, can I tie my new dry return into an existing dry return (the one from that closest main) if I use a loop seal? This would basically make a figure 8 (loop on a loop, with a loop seal separating the returns). I still would add a riser vent for balance.

Now option 2 will cost me a lot more and I may not even be able to route the pipes because of the uninsulated space below these radiators and because things are very cramped in my basement ceiling - it is a rats nest with 80 years of the history of wiring and plumbing.

Can someone tell me if option 1 sounds reasonable? Will the riser vent help the balance but contribute to water hammer in the long counter-flow?