External antenna for GL-E750 (MUDI)?

I’m curious to get some insight or instructions how to open the case to either replace the LTE modem or add external antenna. Obviously there are three screws under the sim cover that help hold the cover on but the case is still tight and I’d rather not crack the plastic. If there are more screw holds or the seam is just being held with teeth along the edge?

By the way, even the stock sim cover is too tight, it should be easier to open. I have filed one the teeth down a bit just to avoid this frustration.

Opening the case should not be difficult. Have to try.

The antennas are all have uFL. But to connect them out, you need to drill holes on the case which is the difficult part.

Are there more three screws holding the back of the case on?

No. Only the three under the SIM cover.

Thank you, that is perfect to know!