No screw holes?
Nope, I've found that the mere connection into the breadboard/connector has enough hold. Even shake it wildly and it won't budge.
A slightly updated version of the DroneCell will be coming out via DIYdrones soon, I'll post when it comes out. I've already tested the prototype batch and the newer ones are awesome! We updated the module to a newer version, so it connects way more reliably and faster. It was a pin-compatible module upgrade, so the board remained pretty much the same ( a few little bonus features were added). Also, the software interface remained 98% the same, I'll be compiling a new library ( for AVR C and also for Arduino!) in the near future.
Also, if someone wants an older version DroneCell, I have a few on hand that I wouldn't mind selling. Send me a private message if you're interested. Price would go for around $85 ( $15 cheaper than online).