Onebyone

I have the older model. The repairman lengthened the amount of thread when using the thread cutter and it has never come unthreaded since. So it can be done. Be sure not to use any but solid bobbins, not the type with holes all around. I really messed up my machine using the right size but wrong type of bobbin.

mamagoat2

I love mine. It has a powerful motor and sews great, whether piecing or FMQ on or off a frame. I don't mind the bobbin placement and have no problems with the thread cutter. I don't tend to use the needle threader but for some reason I this one is easier for me to thread than front-facing needles. The machine is heavy with good suction cups so you won't be wanting to move locations very often. The speed is all controlled by the pedal- no button to govern speed- so be prepared to attach your own to the pedal if that is an issue. It has plenty of speed yet easy to sew very slow when needed without anything extra.

Peckish

I use a 12 or 14 for piecing. Back when I quilted on it, I used a 16 or 18.
When you say your stitches are not connecting, what does that mean? Are you getting skipped stitches? Can you post a picture?
If you're getting skipped stitches (some stitches will look huge) and you're quilting, you need to use a larger needle. The pushing/pulling of the fabric through the machine will cause the needle to flex. A bigger, sturdier needle will stop needle flex.