Help-Torp Depth/Sinking Escorts

[XonE:32]

Noob question. Seems like all my questions are such as I've just started playin' SH4 after a loooong break from SH3.

I'm running SH1.5 UBM + RFB 1.52 + RSRD. I don't know if this is an SH4 thing or a mod thing and that's why I post it here as opposed to the RFB or RSRD forum.

Re: Trying to sink a minelayer leading a small convoy NW of Vigan during my 2nd Patrol out of Manilla @ 0140 Dec 24th, 1941.

Issue: According to the Rec Manual the draft of the ship (can't remember name, but will post it once I get back in game) is 9.6 ft or meters (will check). I know it's 9.6 and I assume that it's feet.

I'm still unsure, but I think the rec manual is supposed to be NOT 100% accurate to reflect the lack of intelligence during the period. With that in mind I always set my torp depth above the Rec Manual Draft Depth.

Problem: Even if I put my torp depth at the closest to the surface as it can go it can only go to about 3 on the dial. There's no numbers on the dial between 0-5. So I set the depth to closest to the surface I can and it still goes under the minelayer.

Is this a bug? (I doubt it).
Is it an RFB thing?
Is it because I'm submerged as opposed to shooting from the surface?
Is it even possible to sink these low draft vessels with torps while submerged or on the surface?

Any help would be greatly appreciated. Usually I just go for the merchants, but I don't run into many convoys and I just thought this time I'd try and take out the 2 escorts first.


Regards

XonE:32

Edit: My mistake, it's a minesweeper with a draft of 6.1 and it is feet. But the .jpg below shows I can only set the torp depth to about 3ft. Is this intended?