In your case, I agree, so carrying some wheel chocks is the way to go. Many Euro cars with the same jack scenario have the same problem.
Another alternative to a 2 ton jack can be found at www.airjack.com.
This is a rubber jack, 12" in diam and operates off a 12v air
compressor. Handy for many uses.
300SE, 300CE, 190/5.0