Toyed around some more with the adaptive filters.

Execution time:

nTaps    Downsampling factor     Execution time average / max in ca. 3 min [us], (480 us available)
1000     16                                110 / 150
2000     16                                280 / 340
3000     16                                380 / 470
4000     16                                Over limit

Now we are running with Downsampling 32, 4000 Taps => max 410us execution time.

I tried to desynchronize the downsampled operations of the filters of the different DOFs. That however increased execution time by about 10%. So I undid that.