Vela....The problem is that most tyre/exhaust/non-Alfa mechanics look at the arrow on the sill and think that is in line with the jacking point on the sill.....It isn't!
If you are going to use a trolley jack on the sill it needs to be as close to the wheel arch as is safely possible. The same goes for both ends btw.
What we do is put some rubber protection pads between the jack and the sill and by far the cheapest solution is to use floor cable conduit and cut it into squares,,,,,If you get a sharp Stanley blade and cut open where the cable is supposed to go and it sits very nicely on the sill.
The rubber/conduit stuff is what they use on stages and building sites to stop people tripping over loose cables.....Like a very flat triangle in section so that wheels can go over them....You know what I mean!