4.5lbs too light? Maybe for one of my revolvers :-P
I do have a little difficulty stabilizing off hand with a Marlin 60, it claims 5.5lbs bare if I remember correctly, but the balance is quite close to the trigger for the newer models. Absolutely DREADED offhand shooting with a forend-less mountain takedown rifle.
I'd play with the balance point as much as I did the weight. If you can keep the balance out front far enough to lock down for off hand shooting, you could go a little lighter and still not feel as light.
Then of course, balance your recoil too - I assume you're talking a substantial brake on these unless the cartridge is quite mild. I'd rather carry a 10lb rifle I can stand to shoot and practice with than a 5lb 7mm mag which beats the he11 out of me.