Hi ManiacYou're forcing me to think.I too had noticed the table depression on the JJs.For that reason, mount ligs. I had one on a Wolf Tayne piece that was very coarse and very difficult to use. If it's too coarsely threaded, you'll be muscling the screww too much based on my experience with several diferent kinds. If you go after the single screw lig, again - make sure it's finely threaded enough that you can secure the reed properly. I don't know if shelling out the bucks for a Francois is worth it over paying a mere $15 for a Bonade inverted lig. I think it's not so much a matter of design, but more a matter of contraction after machining that causes this phenomenon.I reface mouthpieces, so I'm not bashful about flattening the table if it needs it, but you can really screw up a mouthpiece easily if you make the wrong move or don't do it evenly.So I do like the single vertical screw ligs, though I use standard Rovners as well. I've not tried Vandoren's Optimum lig, but it appears to have a similar type of directional force on the reed.If you're not getting a good seal, it is possible that the table of your mouthpiece isn't truly flat, which I've noticed with modern machined hard rubber mouthpieces. The Rovner Eddie Daniels and Bonade ligs (with the little rails) hold the reed similarly. I do like the response from those types of ligs. I have an old Selmer lig that has a similar design. I do really like the Otto Link STM or Strathone Ajustotone type lig with the single vertical screw - so long as it is threaded finely enough to get a decent grip. I'm not good enough for it to matter, I suppose. I use them on SATB and haven't found anything else to make a whole hill of beans difference. (sometimes that's a desired effect, but not normally).

I like Rovners because of their ease of use, but you have to be careful not to get too close to the vamp or overlap the vamp or you can kill the response. To me, reed variation more affects tone and response than which lig is holding it down - for the most part.

Dolnet saxophone mouthpiece