The motivation to make your own battery pack could be:
Need special design that fits in special homemade designed plane ?
Just got some single cells cheap ?
Battery packs are often more expensive compared to the number of single cells.
See the measurements
Weight: 177grames for the entire pack.
Length: 120mm. Width: 35mm, Thickness: 17mm
8 cell pack gives 14A at 8.5V loaded, including cables.
Soldering of the cells was made using special hammerhead solder tip om huge powerfull soldering iron.
The cells was cleened using sandpaper first.