Crew detection distance for watch and sonar

[CrashDive]

Hello all, I just got into SH4 and I am cruising the Formosa straight and noticed a reading on the sonar (green light). After following the merchant contact and closing I could clearly hear her screws at 7-8 nm but my sonar man can't detect anything.

I am now running parallel to her (surfaced) at a distance of 6nm while moving to get ahead into firing position. It is 6am, the weather is clear, no precip, no fog with a wind speed of 0 m/s. I can see her masts, exhaust/smoke and some of the deck using the binoculars. My deck watch crew does not detect her at all.

Clearly my guys are useless and I am a one man team.

My question is... what have people found to be the detection distance for the deck watch and sonar man under these conditions?

I can live with the sonar but the deck watch crew needs to shape up or I am going to throw them overboard. I can only imagine closing on a DD while in the control room and they don't notify me before the DD is already on an intercept course.

Using mods:
TMO 2.5
TMO 2.5 small patch
RSRDC for TMO 502
RSRDC v5 patch1