Hi,
I recommend that you do some accurate drawings of the table to study the proportions and other issues. As a rule of thumb for a 7-ft. Table, the support panels below the top probably want to be placed 20-24" back from the ends of the table. In addition, the support panels want to be held back about 10-12" from the sides of the table, so your guests don't hit the supports with their knees. But, you definitely need to draw this table at a scale of at least 1"=1'-0", and test out every dimension using your current table as a mock-up. Good luck!
--Nils Finne, AIA

Nils Finne has provided some excellent tips. Have you considered sourcing the chairs prior to have the table fabrication finalized? You may be able to gain some flexibility in the placement of the table legs by incorporating concealed steel bar under the table top and in the legs.