I had the triggers on my sabatti 9.3x74 adjusted down to about 3.5 lbs .if yours are crisp at 4.5 lbs im not sure I would mess with them , mine were quite a bit heavier than that .the man that did mine made it look easy but it is not anything like adjusting the trigger on a bolt rifle and should only be done by someone who knows what they are doing as it involves filing the sear .

I read in several places that doubles are commonly set with one trigger lighter than the other with the idea the lighter trigger is to be pulled first and the heavier second trigger helps prevent doubling . the old smith that did mine insisted that both triggers could be set the same and it has worked fine for me for several years now . in heavier calibers with more recoil the chance of doubling is probaly greater if both triggers are the same light pull unless you have a rifle with a intercepting sear .

I don't know anything about your chapuis or how its action works but your triggers probably could be tuned by a competent smith . I will say again that I would be comfortable hunting with a gun that had a crisp 4.5 lb trigger . others here are much more knowledgable than I and could explain all this better .

good luck on your hunt!