10 years ago, I shipped a Mesa Boogie Mark III combo in hardwood cab with EV 12 speaker (read: heavy) from AZ to NJ via UPS.
When it was picked up, I had the driver inspect, approve and sign off on my packing job. And I insured the shipment for its street value - at the time about $1,000.
Unfortunately, the amp arrived at its destination in pieces.
Fortunately, I was able to recover some $$ for damages, but not the full amount, and not without some hassles. Center to that discussion was the quality of my packing job.
I'd opt for having UPS pack it and keep your proof that they did it.