You can use it. For the Maslow it should be OK. Just keep collet and reducer clean.
FYI, on professional high-end cnc, the use of reducers it debated. Some see a potential risk of damage due to unbalance, others use them. Due to the low feed-rates and rather low RPM with the Maslow, I don’t see much risk. If there is an unbalance, the cut thickness will be slightly larger, or the bit will break.
Kind regards, Gero
I use a 1/2" shaft with a 1/4" collet with the 1/4" adapter to 1/8" with a 2 flute upcut. If collet is not tight enough, the bit will slide and then it snaps and that isn’t any fun. Only broke 1 of the 10 bits I have and several have been used up, so it is working.