Here are specs for turnbuckle for 5/32' wire. Breaking strength 2800 lbs. The 1X19 wire in 5/32" 316 steel is around 3,000 lbs. In 302 or 304 steel it's around 8,000 lbs. (I didn't realize there was such a difference). You can, of course use a larger turnbuckle but it has to screw on the swaged stud. Sizing the turnbuckle for 8,000 lbs would be massive overkill.
15% of 2800 is around 450 which seems reasonable.
Check out our Turnbuckle Toggle Assembly Jaw to Swage for 5/32
www.westmarine.com
Specs curtesy of West Marine and are quoted as approximate and subject to errors in my memory as I toggle back and forth.