So, I bit the bullet and purchased the racks by Parttech Ltd from eBay. (https://www.ebay.com/itm/FORD-TRANSIT-CONNECT-ANTI-THEFT-ALUMINIUM-CROSS-BAR-RACK-75-KG-GREY/223320720321).
First, they arrived well packaged from the UK. I should have taken pictures, but I didn't get any until after install. The crossbars come in multiple pieces. The extruded aluminum bars come with a plastic wrap on them to prevent marring the finish. You attach each of the ends on the bar, which allow for about 4" in total leeway for the vehicle width. In my case, they needed to be almost as short as possible, which I would think only adds strength to the connection with the end cap. Each end cap has a single socket head screw to loosen the clamp to attach to the flush rails (Allen keys are provided). Tighten up each screw. There are 4 plastic inserts which go into a slot to cover the socket head screw. Then a locking cover goes over the end to prevent removal of the bars. Pretty simple install and they feel pretty secure. To give a quick check, I put my elbows on the roof, hands under the bar and tried to lift (kind of like a lifting curl) the bar and it didn't budge. Took it for a quick highway spin. There is a little wind noise, but I think that is to be expected with most bars.
Also, a few other notes about the bars: 1) They are tear drop shaped (which is I think similar to the Thule Aeroblade Edge bars). 2) The bars are about 2.7" wide and the usable length of the bars is around 41.3".
I've attached a few pictures, so people can see how they look and how they clamp under the lip on the flush rails. I'll post more comments once I put on a kayak rack and see how it performs.