The Reese Strait-Line doesn't come in a 1,000lb rating any more....., from an 800lb rating it jumps to a 1,200lb rating.
IMO you would be fine with an 800lb rated WDH, even if your TT loaded weight was at it's GVWR of 5,900lbs ......., I would just visit a CAT scale and confirm that your loaded tongue weight is at/under 800lbs (or adjust accordingly).
FYI: If in fact you did maintain a 885lb loaded tongue weight, a 1,200lb rated WDH would worked if it was adjusted properly...., being 300lbs over-rated may influence a little stiffer connection, but IMO isn't overkill with a 885lb loaded tongue weight (but a 1,000lb rated WDH would be 'ideal').
If you would feel more comfortable with a 1,000lb rated WDH do to heavy loading habits, the Equal-i-zer brand WDH comes in a 1,000lb product. The Equal-i-zer product also incorporates integrated sway control as well.
Also, check that there isn't any WDH rating restrictions noted on the TT's A-frame.
CAT scale how-to: http://www.jaycoowners.com/showthrea...igh-Your-tt-tv