There are a few easy mods to do to enable the seat to slide forward.
Both units are a a couple of inches too wide so you need to reduce the width. To do this I took this out the middle of the 4 aluminium width poles and then shortened the table width by removing the aluminium slat end holdings and hacksawing off the required amount. Putting the mouldings back and then just denting the aluminium underneath to hold them in place, To keep the strength I use a cut length of dowel or in my case about 8 inches of a suitable diameter broom handle and some gaffer tape. (It's hidden in the canvass). The canvass surrounds can accommodate this mod as the drawers are a lot shorter than the width available.
To stop things sliding off I use Ikea door handles. It's simply a few drilled hole in the aluminium.
http://www.ikea.com/PIAimages/81928_PE207208_S3.JPG
I also reduced the height of the table top to level with the window by taking a couple of inches off the upright poles. Again the drawers can accommodate the mod.
I keep the legs under the table tops as there is a gap.
If you want help or exact measurements just contact me direct.,