Yes, bed speakers 4-5' to tweeter.
Front 3 in a row at tweeter height if possible. Matched speakers even better.
Pretty sure budget allows for 3x VP180 as vertical channels. That would be something I would say!
Just buy aftermarket brackets (like french cleats) and use the T Post as electrical connection block only. The T Post is a super ingenious design, but I can see a long speaker being a little nerve wracking.
I've used these before. Work great.
Cleat:
https://www.amazon.com/BIGTEDDY-Picture-Hardware-Aluminum-Mounting/dp/B07C4H9YK1/ref=sr_1_6?keywords=french%2Bcleat&qid=1639309660&sr=8-6&th=1
