Personally, I’d give the wire a little headroom. 16awg is a fraction more expensive. And you’ll be surprised how the small distances add up. It’s not calculated just to the connector.
Plus, I think it’ll be just fine on the bike. Remember, you’ll never have full beam, side lights, brake lights, horn, hazard lights, indicators, electric start, ignition lights, neutral light etc etc all on at one time. Also, they get too toasty after a little while so won’t be at max either.
OTOH, have you thought about rechargeable heated clothing?. My sister had horses and regularly wore rechargeable heated coat and gloves. They lasted all day and got too hot so were never on max.
Martin
All makes sense. Big thanks.