always used a rack for cycle camping, just wondering if a small tent will sit under my jones bars?
it only weighs a bag of sugar and half. should be ok?

My partner has Jones bars and can get a 2 man tent and a pot and 2 mattresses under them. Works well.
http://www.farawayvisions.com/whats-ins ... king-bags/

I have Jones Bars and my Terra Nover Laser [tiny] 2 person tent with tarp and waterproof fit under modestly, could easily take more, but as I have Anything cages on forks, dont want to add too much weight on front.

Go for it.

Should be fine, I've quite happily strapped a tiny 2man tent on top of the stem/bars with normal risers and there's a lot more space under Jones bars.

This weekend I had my Lunar solo, my Cumulus 450 and 250 quilts in a dry bag while fixed to my Wildcat harness on my Jones H Bars and the Lion never missed a beat.

No problem! I carried a standard size quite heavy 2 man tent to Bearstock and barely noticed it was attached to the bars.

The truss on your plus definitely takes up some space which would otherwise have been used for kit, but on the other hand, it also keeps gear off the head tube. You shouldn't have any bother getting a tent under though.