15m antenna?

Judging by the results on FT8 RX today with my very improvised 15m antenna, I am tempted to convert my Par end fed antenna to 15m. 

I suppose I could make it cover 10m and 15m by putting up 2 wires. Already today, I have spotted 350 stations on 15m FT8 RX. Don't forget that some of the time the PC had closed down with a flat battery too!  With a "proper" antenna , I would expect even better results.

All that should be needed to cover 15m is a longer wire.