HB Side Imaging does well at TM speeds as long as the Chart speed is set to match boat speed ...
Turning the TM with a SI xducer attached does affect the image ... as long as the TM is kept straight when you want pretty internet pictures ... and then understand what the "smear" is when turning the TM ...
(See the 3 fishes at upper left after I turned the TM and caused the SI to smear?)
Rickie