what are the ups and downs that you encountered and how’s your tank now and what would you have done differently?
I've built several stands over the years in this hobby and RocketEngineer's plans are a great baseline and sturdy.
I recommend making your sump easy to access, as in removable panels instead of hinged doors, so you can get in there and do stuff when you need to. Frame it, skin it, and put panels on the sides and front, etc.
Someday, you will need to get to that spot you don't think matters right now.
Leave some openings in the back so you can run cables, hoses, etc. But also those openings provide gas exchange for the sump. Add openings in the back/bottom so if the sump overflows, or you dump water, it drains and doesn't flood your stand. Basically, I skin the back with a sheet of ply leaving a 6" gap on top and bottom. Top for lines and hoses, bottom gap for water.
I run my sump 'cryptic-ish'. No light down there. So, the sump stand interior I always paint a bright white so I can see stuff.
Also, think about your sump and how you will access it. Think about how much height you want so you can work on stuff. My last two builds, I made the stand way taller than I had in previous builds and I'm much happier as I can work on gear, put things into the dungeon, etc. without being a contortionist.
One last thing. Consider your sump and how it will fit into your stand. Don't build your stand and not ensure you actually fit the sump into it. Sounds silly but...