I would have used spa tube.
I put hard foam under my stand and under my tank.
I always use a couple of inches of flexible tubing from my pump to fuge hard connection, cuts vibration. I also put car wash sponges under the pumps to cut vibration.
I would have used a reculating skimmer, will build a raised rock bed, and would have a built-in sump fan, instead of clip-on, takes up to much space. Would have planned the sump better for a dsb, no algae, to keep dark. I now have an exterier, dsb in bucket, and yes!!!!, 3 1/2 weeks later, All of my corals polyps are out, and happy. (Save for another thread)
My sump is in stand, and raised on acrylic bricks, incase of mishaps, water won't get trapped between, and can evaporate, not rot (I know, ya not supposed to have a miss hap, yea right) I would look to the worlds end for quiet hood fans!!!!!!!! Anyone!! Anyone. I would have built the hood differently, and added moonlights.
I will use multiple switched power strips, like the group buy, best change I made, But I will plan a lot better for ALL electrical connections including the future ones (Isn't that part of initial planning, LOL),, and use the electrical grease on plug ends.
I WILL PUT EVERYTING IN PLACE, BEFORE FINAL HOOKUP AND WATER (repeat this line, repeat this line, and repeat this line....)
I will place items, pumps, skimmer ECT, ECT, for better access and maintained.
I won't buy equipment, before measuring its placement!!!!!!!!!!
I would setup sump for probes. Don't skimp on bulkhead quality!!!!
Check, double, triple, then start again, each and every piece of equipment SEPERATLY, FOR LEAKS , NOISE, FLOW ECT.
Not have equipment tied into another piece, without have a contingency plan for failure, and testing the theory, BEFORE, it happens