Derby to me at that time of year is - jewies, golden snapper, scarlets. Creeks are full of jacks and mud crabs
It's a fair run to get quality bottom fish and have only ever gone during neaps.

If you mean Derby town, you would be a long way from Red Emperor waters I would have thought. I would think you would have to exit King Sound first. The muddies waters of the sound will hold plenty of good fish but I doubt reds would be on the cards. In Broome waters the Reds were a long way out and not all that reliable.

 We will be heading to horizontal falls/Montgomery reef. Appreciate your knowledge 

Certainly no expert on that area but I don't think Reds are going to be your target there...but could be wrong. You are better targeting big fingermarkk and Jewies as Norun Nofun said.

I would say to go up there with an open mind. As far as bottom fish goes its very tidal. If your only goin for a short time I would say go for the scenery fishing is a bonus. Everything revolves around the tides you may only be able to fish the bottom for 2 hours of the tide.  Your most likely to catch fingermark and scarlets whilst bottom fishing  One thing I can say is from looking at nothern territory studies these are 2 species as well as jew are not good targets for  catch and release as they suffer badly from baratrauma.   As far as barra go around low was the go. But beware make sure you have a creek exit plan in place. We once got stuck in the big boat 19ft on a side creek and ended up on a stupid angle losing  50l of fuel out the breathers and a 3 hour wait in 40 degree heat for the tide to come back in. Just a question to someone who might know can you still get fuel from dog leg creek? I was told both cockatoo and coolyn island are now shutdown.

I would say to go up there with an open mind. As far as bottom fish goes its very tidal. If your only goin for a short time I would say go for the scenery fishing is a bonus. Everything revolves around the tides you may only be able to fish the bottom for 2 hours of the tide.  Your most likely to catch fingermark and scarlets whilst bottom fishing  One thing I can say is from looking at nothern territory studies these are 2 species as well as jew are not good targets for  catch and release as they suffer badly from baratrauma.   As far as barra go around low was the go. But beware make sure you have a creek exit plan in place. We once got stuck in the big boat 19ft on a side creek and ended up on a stupid angle losing  50l of fuel out the breathers and a 3 hour wait in 40 degree heat for the tide to come back in. Just a question to someone who might know can you still get fuel from dog leg creek? I was told both cockatoo and coolyn island are now shutdown.

 You can get fuel at dog leg creek but you have to book and order in advance 

thanks for the info