Hooking an Ext Cab to my Ace Combo

[StaticRoute]

I have a Stiletto Ace 1x12 combo and a 1x12 cab. The cab is 8 ohms and I assume the speaker in the combo is 8 ohms since that's what it was connected to when I got it. I'm guessing in order to use the cab along with the internal speaker I should move the internal speaker to the 4 ohm jack and plug the cab into the other 4 ohm jack. The problem is I can't easily unplug the internal speaker from it's 8 ohm jack without removing the top back panel. I've tried it with them both plugged into the 8 ohm jacks and it sounds good. Will the mismatch be a problem?

 

[plan-x]

I didn't see that one in the manual. But if you get the time, remove the back, to accomplish the 4 ohm, double hook up. It should sound a little better(fuller/louder) and is a perfect ohm match. The speaker ohm diagrams start on page 27 of the manual. Here's the link. http://www.mesaboogie.com/manuals/stl_ACE.pdf