iceperch wrote: I'm just paddling.And my yak is not an inflatable one.

I don't understand what you mean by style of mapping.

My arm mount is made of aluminium/Pvc/printed PETG PARTS.
I CAN tilt and vary any angle I need.

Anyway I think that I should try the Team Colibrì suggestion to try and use another sonar preset.

I think that TeamColibri got the right suggestion.

Right today I went out and used the DeepWater Sonar Preset
And this is a screencapture of part of a log. It seems much more accurate than before.

One thing that I do notice is that the secondary sonar channel is missing. This also happened when for the first time I used the General Use preset. So I may consider that this is another undocumented feature.
Am I wrong?

Still about the central part of the sidescan: I continue to see distorsions. Could it be because I'm not taking advantage of the RM features related to hardware acceleration?

Are You sure that Your cayak is balanced during paddling? No tilts? Are You measured it some applications or spirit level on water?
Style of mapping- for me it's driving across water, paralel tracks, only for grabbing data- not fishing. Inflantable boat is better for one reason- vibrations are weak- it's improving mosaics too, but if You paddling - It's no problem with that. Despite of this- no matter what boat, problems with pings are from ducer mount primary, secondary source are sonar settings. Before buying Simrad Evo3 I used HB Helix, and pings from it needs fix too, more than EVO
Next time on water- please small thing: try paddling across water, only two tracks and check it.
If You want- I can check Your sonarlog with SonarTRX which is designed for sidescan maps, got powerfull tools to slant range correction.

is there a demo version of SonaTRX?

I have discussed this with Matt over the years and have sent him a detailed breakdown of how I would love to see ReefMaster evolve in this department.

With some effort great results are possible with SonarTRX, but unfortunately Tore no longer offers support for his product so that is the end of SonarTRX.

At around 1min10sec you will see the FishTec HD Mosaic Chart -

Here is another one on Facebook -

Click Here

Here is another example of a chart from a while back without too much 'cleaning up' -