Yeah,you can put 2 plates on the Smith machine to do bench dont
mean a sh-it...dont mean you can do 2 plates on a barbell.
The bar on the Smith is NOT 20kg,so dont think you put 2 plates on
it,you are benching 60kg. I think the bar is only
10kg,furthermore,the lack is stabilization is another 10kg gone.So
when you bench 2 20kg plates on the Smith,you are maybe doing only
40kg!
When you been doing machines and decide to switch to free
weights,you will be as weak as a kitten,you can bet your ass on
that statement.
As for machines increasing your bodyweight,they cant do much in the
long run.