Ciampino is long enough for 747s so guess that isn't an issue.
I would not assume that, since the configurations of the aircraft and the subsequent performance may be surprising.
The 737 800 approaches relatively quickly, I believe and it may or may not approach faster than a 747 or C5 and may or may not require a similar or longer LDA. I notice, from the Boeing noise ababtement website, that Ciampino has 2196M available for landing - compare this with Stansted at 3148 and you will see that there is quite a difference.