One the yv666 .. 11000 hull 600 hold smaller than a bwing turns faster than most heavy fighters. For ease ie. no ship model changing of size etc make it truly a beginners freighter 3000 hull 100 or 125 cargo same size turns about same as heavy fighter 1 maybe 2 turrets cost about 150k and max speed about 90.
If you want to keep it at the same stats increase its size alot, make it much less manueverable than it is now, maybe a second slower than the corvette.
Two the corvette NEEDS to lose that engine cut special and its double base speed(say 70 or 75 max impulse). The dual thruster idea on them is good for it to be the "blockade runner" with 120 boost per thrust thats sill a 290 thrust speeed, nothing can keep up while not in cruise.SInce its supposed to be a small cap ship(it was in xwing) make it the most expensive ship most armour say 10k( since theres x3 armour enhancers dont want to get too drastic) a 800 hold or even 1k keep same number of guns triple its size( i remember being able to fly along its bow and shoot at it for a second or 2 before i passed its engines) and cost in the several millions. Of course it may not be able to dock at small bases, unless they have mooring posts, larger bases or planets.
Three sith infiltrator as it is now is a crap ship unless it cost about 100k.
If you want that price tag, same cargo, give it 6 guns not the 4 it actualy has after purchase, make it have a 100 or 105 top speed( not its current 66) and turn faster than it does now, say a little better than the bombers but worse than tie defender slghtly or xwing