Axel - that ought to work fine. I have a similar scale and use it like this:
Set it to grams, set an old Corelle plate and putty knife (or whatever you're scooping/mixing with) on the scale, and press "tare". Scoop part A onto the plate until you've got about what you want evenly divisible by 10, then add part B to the side with a popsicle stick. Don't contaminate one with the other until you're done measuring, 'cause you might be adding/removing B until you get it right. For example: 50g of part A, run the weight up to 55g with the part B, and mix! Even though it's only accurate to a gram, it seems to be "close enough".
Just don't do the boneheaded thing I did: 150g part A, run the weight up to 155g with part B, mix, and install the rear baffle and cleco every hole - before the 2 nagging thoughts "this is too easy" and "something ain't right" came into focus. After talking to a guy in the Flamemaster lab ("It will never cure properly - at altitude the fuel may push through") I took it all apart and thoroughly cleaned off all the sealant. I'm thankful I hadn't started riveting!
The only bright spot in that four hours of wasted motion was seeing that the baffle would have been sealed perfectly.