myson's in a series loop?

myson's in a series loop?

Have an existing series loop zone. Zone has one colder room (over a garage; already sealed, insulated, etc. as best can be done to get the heat loss down).

I need about 1500 more BTUs. Existing baseboard is 12.5 ft of 550/BTU/hr/ft. 1970s vintage "Brand X" fin-tube.

Options I'm presently considering:

1) add another 3 ft of standard baseboard;

2) remove existing, replace with 10.5 ft of multipak/80; or

3) install a pair of Myson SX 30140G's.

Option 1 not favored as we're eating wall space already.
Option 2 doable with relative ease.
Option 3 would look nice in this particular room -- scale, style, etc.

Question is, could the Mysons be piped into the existing series loop? Can these rads be mixed with fin-tube? They would be early on the loop.

The additional head would require a Grundfos 15-58 on speed 2 to satisfy the whole loop at 4gpm if I've done the flow calcs correctly and assumed one diverter tee for each rad as well.

Any insight into feasibility and how to pipe this would be most appreciated.

If there are other options in panel rads, I'm open to suggestions. Just doing recon at this point.

Many thanks.