This is my approach on being able to properly fly helicopters in DCS or Flight Simulator. The system is quite simple, it uses a couple of movement dampeners, cylinder and piston, an it is the friction caused by an internal O-Ring the force that keeps the stick in position. This way force is applied evenly and has no wobbles or weird movements.

It can be fitted and removed to go back to fixed wing pretty quick and easy (just remove the ring base, put the spring back on, and move away the dampeners or remove them completely) No permanent changes to the stick required.

What parts do you need

The MOD works pretty well with just two dampeners, at first I thought about 4 axis but with two it works much better (for me), if you have stick extensions maybe you'll need more force and 4 of them could be necessary, but for desktop or chair mount, two are more than enough.
I included two variations of the piston, one called Smooth, and the other the regular one. Regular one will work better if your printer leaves no layer dents and you use a really thin layer height (below 0.1), they are printed vertically. The smooth ones are the ones I use, as they're printed flat, there is no "sawing" noise and feeling when operating the stick. I recommend to start with the smooth ones.
So, you'll need to print:

• The two rings
• Two pins to attach the dampener to the stick base
• Two cylinders
• Two pistons (smooth or regular)

What else do you need

You probably already have some of this things at home, but if not, you can easily find them at your hardware store or online in your shop of convenience. I've always at hand a box with a big mix of o-rings and a bunch of M4 and M3 screws and bolts of different measures, that's pretty useful. So you'll need just this:

• 8.5mm OD x 4.5mm ID x 2mm CS O-Rings, I think they're called M2x4.5 O-Ring. Each dampener will need one, two if you want extra friction.
• Two M3 screw and bolts to mount the ring in position
• Thick lube for the pistons and the ball joints (this is important as keep things operating smoothly)

How to build it

Follow this easy steps:

• Lube the ball joints, both pins and rings
• Insert the pistons in the pins ball joint
• Insert the cylinders in the rings ball joints. The position you see in the image is the one that works better for me, that is two cylinders in one of the rings (cylinders on the left side of my stick)
• Put the O-Rings in the piston tips (you have two spaces, you can add two O-Rings if you find they have not much resistance to movement)
• Lube the O-Rings and the piston body, and insert them in the cylinders
• Remove the stick spring and mount the handle without string at all
• Screw the two rings in position, there is a small latch in the rings, this goes up and prevents the ring to move down the stick
• Insert the pins in the stick bas, you can use tape or any other means to keep them in position if you find them too loose. If you are using screws to fix the stick base to your cockpit build, you'll need a different measure to keep the pin ball joints in position, be creative! :)

If you're used to centering sticks and the fake trimming, it will take a bit to get used to this, but once you spend a couple of hours loitering around in your huey... yo'll find it perfect for rotatory wing, you'll never go back to spring loaded sticks for your helos!

Here you can see a quick video of the stick in action: https://www.youtube.com/watch?v=uCa7xKkc2Lc