Maruyama Quick Connect is the best and I've used all the Combi systems from every major player.
https://maruyama-us.com/product-category/multi-cutter-systems/
I've been a member of USAA for 30 years. I dropped them 2 years ago because they kept raising my rates for homeowners and vehicle insurance. I switched to Allstate and I saved about $1,200 every 6 months.
Use a strap on the string trimmer. Takes all the weight off your arms and they're just used for guiding the trimmer back and forth.
E.T.A. that I use the Good Vibrations brand trimmer strap.
I just ran it for one year in my 2017 Accord hybrid. In that time, I racked up 7,832 mi. I also did a year on my F-150 5.4, but only put less than 3,000 mi on it. I don't think the formula is much different for the 20000 or 25000 mi variants. I wouldn't be worried about going 8,000+ on your...