Yes it is, the trifold worked very well. However, I had some issues with the plastic case part, very quickly, within about a month or two the plastic started cracking and then proceeded to break and fall off of the case until eventually it wouldn't hold my ipad anymore.
The only slot to connect anything that I see is the headphone slot on top and the ipad charging slot on the bottom, if these are the ones you intend to use your "Square-Up" unit I believe yes you can use it.
It's not about the length or width in this case. The back piece of this case is specifically molded for an Apple iPad Mini. The iPad mini "clips" (for a lack of a better word) into the back part of the case and then the smart cover closes and protects the screen. Had it been a generic case for a 7" tablet, I'd have said yes. In this situation, I have to say your tablet will not fit properly and stay secure like an iPad Mini does.