One key parameter with regards to any tools is to reduce the overhang.
The image shows a simple change in the length of cutter tool that is protruding from the collet chuck, but this small change in length will have a significant impact on the stiffness of the cutting tool.
If the cutting tool is not stiff enough it will chatter and you will have to reduce cutting depth and feed rate.
You can also change the way in which the cutter is held:
The difference in tool overhang when changing from a drill chuck to direct 3MT collets is huge.
This image shows two different setups in my old Amadeal Milling Machine.
All of these changes reduce the distance between the point at which the cutter is making the cut and the bearing in the shaft. If you reduce the distance between the point at which the force acts and the point at which the material is anchored you will increase the stiffness.