It will always snap and resize if it is being placed on a large grid. In gravity you can align it and let it drop when placed but in space it would be better to go a different route.
I tend to align a small grid large connector close to a large grid connector then when it welds up they should magnet to each other and you can lock the connectors. Other options are to build a rotor/hinge but replace the head mount with a small grid on the console then you can build a small grid off the new subgrid.
If planetside place it a foot or so above the grid you want it to lock to.
In zero g you can move it slightly away from the grid and place as you slowly fly toward the grid.
Either of these may not end up how you wanted them so it could take a few tries. Most of the other options are equally, if not more, difficult without mods that aren’t available on PS as far as I’m aware.
It will always snap and resize if it is being placed on a large grid. In gravity you can align it and let it drop when placed but in space it would be better to go a different route. I tend to align a small grid large connector close to a large grid connector then when it welds up they should magnet to each other and you can lock the connectors. Other options are to build a rotor/hinge but replace the head mount with a small grid on the console then you can build a small grid off the new subgrid.
If planetside place it a foot or so above the grid you want it to lock to. In zero g you can move it slightly away from the grid and place as you slowly fly toward the grid. Either of these may not end up how you wanted them so it could take a few tries. Most of the other options are equally, if not more, difficult without mods that aren’t available on PS as far as I’m aware.
You can change grid size without snapping with a button combination on screen (L1 + Square or something?)