I hate to be the bearer of somewhat trivial news but this antenna will far outperform your unnecessarily huge setup. I have almost every antenna available including the 915 MHz 8 Dbi Rak antennas and these cheap little Proxicast wide ban antennas outperform everything in the omnidirectional category.
I have tried that antenna before... it’s like a 9dbi omnidirectional? Try this one and thank me later ;). You will also need these connectors
If you both put this antenna in your second floor window, you will 💯% witness each other.
You will also need these connectors.