We use Mark 4 and HDS-7 units with Lowrance HST-WSBL in fresh water and record to SL2 format. We have used up to now the default Equipment Profile, which sets Cone Angle to 20 degrees, Manufacturer to Humminbird, and (I think) Salt water.
* Is the Cone Angle for this transducer 20 degrees? I have seen 22 on the Lowrance site.
* Do I need to set manufacturer?
* Do I need to explicitly set salt vs fresh for SL2 files?

Salt/Fresh is only required for Humminbird logs, because we need to be able to derive the approximate speed of sound in water. You can ignore this for Lowrance.
Likewise you can ignore the manufacturer field, as this is only used to enable certain manufacturer-specific options, none of which you will need for your unit.
Your cone-angle is fine at 20 degrees.

Thank you for your prompt reply.