Then I shall have to illustrate:
Here's a top view just to give a general sense of scale. All ships are on the grid plane. Note the grid units; each square is 100 meters on a side. Of these ships, the only one with a fighterbay is the Moloch. Let's move our fighters in for a closer look...
Not too spacious-looking, from the top...
I've also provided a side view... look at the heights of these fighters compared to the fighterbay.
Finally, just for fun, have a look at the Erinyes placed inside the fighterbay. The camera is actually positioned inside the ship, as this was the best position I could find to show how much space there is. Admittedly, the Erinyes is of course one of the narrowest fighters, so this is a bit beyond what would be necessary to make my point, but whatever...
To get some empirical data, that hangar is wide enough to fit the length of a Poseidon (about 50 meters), and tall enough to fit the width of an Ursa (about 35 meters). The only plausible reason for there not being fighterbays on cruisers in FreeSpace is the gameplay implications (and perhaps some overestimation of how big a hangar must be, as you have done, and as I did in the past)...
The opening to my cruiser/carrier's fighterbay is about 12 meters by 22 meters... a bit under half that size, but still big enough for an Erinyes.
Nonetheless, I reckon it is indeed too small even for my purposes, and I'll very likely scale the ship up sometime soon -- scaling the entire mesh should be a fairly painless process.
However I should also mention that this ship is not primarily intended for the FreeSpace universe (although I suppose seeing it in-game wouldn't hurt anybody)... I am seriously considering making the hangar be primarily for retrieval, and using launch tubes (like in BSG) to sortie the fighters. This would prevent the issue of "debris on the flight deck" preventing launches (something that plagued the Terran capital ships in FreeSpace 2), and would mean fighters can enter the fray quickly, rather than having to first navigate through a clogged hangar. It'd also be much harder for enemies to disable each and every launch tube than it would be to take a single exposed hangar... although I did make sure that the hangar entrance was placed in a fairly sheltered location on the underside, just to be safe.