Lots of great tips given to you already.
But how about putting encyclopedia books or something else behind your extension table to keep all your work at the same height...then top with vinyl so that all your work will slide away and not drag down?
I'm fortunate enough to have a huge sewing table, 4ft x 8 ft, with my machine recessed to keep everything flat. That smooth even work space really makes a huge difference when FMQ.
warm quilt hugs, sue in CA