moving gantery CNC sturdiness

[RonVais]

Thank you everyone for your fast response !

I'm currently designing the machine in cad but i need to choose my components for the design- so dont worry choosing the compontent doesnt mean that Ill buy the component tomorow before compliting the design

As for the items i have bought are pretty much general use - exept for the spindle that i have seen lots of builds with (also as far as i know plywood usualy is cut at high speeds and those chineese spindle do fine at and dont loss to much torque at high speeds) and for the other parts i just had them already (steppers and steel tube profiles)

The main tree questions for now are:
* Will 50*100*3.2mm steel frame (not welded frame) will be sturdy enough and not vibrate? (as I sayed earlier I intend to build moving gantery configuration CNC with the dimentions 1500*1500*300mm of the frame)

* Can i get off with the kit mentioned in the original post? it includes HGR20 rail and HGH15CA carts
and a 2005 ball screw ( i understand the 2010 will be faster though i can compensate with driving the steppers at higher speeds to reach 100mm/Sec)
a kit with 2010 ball screw at aliexpress is about 250 euro more exprensive

* Will a ball screw at such length unsupported be sagging? and what can i do about it? (i dont want to use the rack and pinnion systems cause they are more expensive )

Thanks!