Ah IC. A durso is the easiest type to make and typically pretty quiet.
Pretty simple to make but the key is to reduce the pipe size after the standpipe. So If you have a 1.5" Bulkhead in place already you should make a 1.5" Standpipe. Typically you would then drop the pipe size to 1.25" below the bulkhead to the sump however since it's only a 35 gallon and your flow rate is going to be fairly low you should drop it to 1".
If a 1.5" Standpipe won't fit in your overflow a couple bushings in the bulkhead will allot for a smaller standpipe. You could go as small as 1" for the standpipe and 3/4" for the drain line below.
If the durso design is just too big for the overflow no matter what look into a stockman or HGB.