R-300 Sump (Specific) Dimensions?

Will i be able to run a DSB? or should i just do SSB

 

It won't allow you to go very deep because of the slit as you've speculated; you could maybe get 3" in there, see below:



I'd keep it shallow.

Here's a picture of my R-300 running. You can see the water level is a little higher in the skimmer section than the fuge, but this is due to me running a high amount of flow though the sump.

 

does the return pump section run a little lower than the rest of the refugium? just trying to calculate for any back siphoning if there is ever a power outage. i plan on drilling a siphon break but like to have a clear mind knowing that if the siphon break fails i still have room for water to run back in

 

It must for the whole thing to work right.

The blue "Water Line" sticker you see in my photo is the suggested height there.

 

are the brackets on this big enough to redrill for a 1 1/2 inch bulkhead?

 

"Should be". Here is the bracket on my R-200:

 

is only 3/4 of the bulkhead on the bracket to start?

 

Basically, yes. That's about as far in as you can get them. They are gravity fed of course, so they aren't going anywhere.

 

starting to worry now that i screwed up ordering this. My overflow uses two 1 1/2 inch drains and i need to either reduce the drains just before the fuge or redrill the fuge to take 1 1/2 inch bulkheads

 

I would just reduce. You can use reducing bushings like these: Amazon.com: PVC REDUCER BUSHING 1-1/2 X 1-1/4 (Like CRL E950HG): Everything Else

The sump comes with 1 1/4" flexible piping anyways, so just use the reducers right after your overflow.