Wirewalker buoyancy foam

We ballast the Wirewalker to have about a 0.5 meter per second ascent rate.  We simply add or subtract foam blocks (the lower center column is a good place to start removing foam). We have a test pool where we lower a cable with a bottom turnaround stop down and small weight to the bottom of the pool.  Keeping the weight just off the bottom we deploy the WW and manually raise and lower the cable simulating wave action to walk the profiler down.  When the bottom stop engages the cam we start a stop watch.  Our Wirewalker travels 9m in our 10m pool and we aim to add or remove foam until we achieve roughly 18 seconds from the time it starts to rise to the time it breaks the surface. I'll do it about 5 times to get an average.  When in doubt aim for the faster ascent rate, as it gives a more positive hit on the upper stop.