Welcome to the Jayco forums.
This is representative (in blue type) of the information Jayco put in their brochures/website about your 2008 29D:
Unloaded Vehicle Weight (lbs) 5,810
Hitch Weight (lbs) 875
Gross Vehicle Weight (lbs) 7,350
Cargo Carrying Capacity (lbs) 1,535
Exterior Travel Length 31' 1"
Exterior Height w/AC 125"
Interior Headroom 78"
The hitch weight (tongue weight) of 875lbs is based on unloaded (dry) conditions. When looking at proper sizing of a WDH one should work with "loaded weights", not dry or unloaded. The loaded tongue weight of a 30ft. TT should be 13% to 15% of the loaded weight of the TT, but since you don't have any CAT scale weights under loaded conditions, we will assume
the loaded weight.
Loaded 29D weight:
(5,960lb ship weight) + (150lb battery, hitch, dealer stuff) + (700lbs cargo & stuff) + (no fluids) = 6,810lbs loaded
Loaded 29D tongue weight:
(13% to 15% of 6,810lbs) = 885lbs to 1,021lbs
Based on this weight range a 1,200lb rated WDH would be fine. A 1,000lb rated would WDH work as well, but Reese recently stop making them (?). The 1,200lb rating will also cover the 29D's GVWR (in case of heavy loading or carrying fluids). An 800lb rated WDH would be to lite. Also confirm that your TT A-frame doesn't' have any WD size limit stickers.
Round bar versus Trunnion bar WDH's:
They both provide the same weight distribution results, but their different configurations have unique clearances advantages with different TV/TT combinations. The one advantage the Trunnion bar set-up has is that the ball mount provides more tilt adjustment.
Reese Dual Cam or Standard Reese Friction Sway Bar:
A single friction control sway bar is recommended for trailers up 25ft in length, or add an additional sway bar above 25ft., and these devices have to be removed when backing up. The Reese Dual Cam is a more effective means of addressing a sway event, especially with the longer TT's, and doesn't have to be removed when backing up.
The 29D TT has a lower profile frame, ball coupler mounted to top of A-frame, so IMO a Round Bar WDH would be the better choice. The Dual Cam would be a better form of sway control for the 29D's length.
My recomendation: http://www.etrailer.com/Weight-Distr...e/RP66078.html
Hope this helps.