Looking very nice so far.
Some firmwares on other devices I have will allow you to hide system or notification bars in settings. Maybe this feature can be added by Khadas to their next VIM3 firmware.
It maybe possible to modify the build.prop file to hide them, but I do not know how.
Maybe @goenjoy can offer you some guidance.
It may be that a custom firmware(ROM) by superceleron has the feature, I can’t recall. I will try his ROM on my VIM3 and check for it. It will be tomorrow night before I can do it. If you are curious about his ROM, see here.
As for the soldering, remember to first tin the leads and the pads, that will reduce the amount of time needed to heat the joint. If possible, set your iron to just above the lowest setting that melts the solder you have. Low temp solder and also low temp solder paste are available.
Looks like 2.5mm…