Can I use just half the biwire?

I would just buy one pack of the attached.  On each speaker post you would use both one of the banana connectors already on your wire and also one spade from the banana to spade connector.
https://www.amazon.com/dp/B00X9FET7I/ref=sspa_dk_detail_1?psc=1&pd_rd_i=B00X9FET7I&pd_rd_w=y...

This is if you don't want to cut your speaker cable.

@ scott_w

I also agree with lowrider57

Something no one has mentioned, will the un-terminated ends of the bi-wire cable work as an antenna and introduce RF back into the output of the amplifier?

You might want to send a PM to almarg and ask for his thoughts.

Same question was asked last week - most binding posts will accept two bananas one in the bare wire hole, one in the banana hole
https://forum.audiogon.com/discussions/please-help-me-clean-up-this-stupid-speaker-cable-mistake/pos...

Thanks everyone! Good info.