Richardson system venting

Fizz

Richardson system with 2 loops. Larger loop has 4 rads attached with 137 sf of radiation; shorter loop has 10 rads with 343 sf of radiation. Large loop runs 41' with one rad on 2nd fl; short loop runs 35', but has drop down and 25' run-out plus 16' lateral with riser to 2nd fl, a lateral off of this lateral of about 6', 2 more laterals off this main one is 9', the other 6' to riser to 2nd floor with 2 rads attached. Both loops share single vent, while the 25' run-out which has 118sf of rad(included in 343 figure) has it's own return and vent. System works fairly well-larger loop rads heat quicker and better,
Richardson specifically called for separate vent on each dry return. Wondering if adding separate vent to short main is practical. Short main has about 14' run to drop-down to wet return.