Only problem I see so far is that the 30 gal may be too wide to fit into your stand, if they're the dimensions I am thinking of. This is easily overcome in DIY stand.
Some things i learned while setting up my coast to coast:
1. Plan for return line placement. Sounds dumb/no duh right? Well I overlooked it.
2. Don't do true coast to coast. Because of #1, what I would suggest instead is that you leave space on the sides to have holes in the back glass for bulkheads controlling returns. So your overflow box would be like 85-90% of the back wall.
3. There are more flow options in 1/2" loc line than in 3/4". This is important only if you get nervous about putting painted plastic in the tank, and want to black everything out.
4. Loc line is expensive! So don't overlook #3
5. Go external! External overflow boxes are much nicer. Learned this one after I already ordered. If you go external, you can drill in the bottom of the external box, so make it deep enough for upside down U with the screen attachment. If you can't go external, make the box as narrow as possible, and deep enough to use the screens you can buy, or else you will be doing a lot of cutting.
6. As narrow an overflow as possible. This deserved its own, even though it was mentioned in 5. Narrow overflow reduces impact on footprint, blocks less light and flow = less algae problems and more scaping options. Conversely you could just do a whole back wall overflow with single pane of glass, but 55 is already pretty narrow.
7. Have 2 returns. You will need to point one underneath the overflow overhang to avoid issues. Also gives you better distribution if you decide to inject co2 into the sump later
8. Glass is not the same price everywhere
9. Wish I would've made the sump out of acrylic
10. Easier to design the sump the way you want it, then find a heater that works, or go in line if you have to.
11. Leave enough unused volume in sump for drain off in power outages.
12. Your sump should also be level
13. I am torn on sponges vs. Socks as I have only ever used sponges, but people seem to like socks. I saw a mod where you cut slits in the top of the sock, then put the outlet lower than cut so that if it clogs it just runs through the slit instead of onto the floor.
13. The way I wish I would have designed my plumbing, no drawing tool so bear with me. Stand pipes exit the center back of tank, and feed into center section of sump, directly onto stacked filter media. Bubble trap on left side separating return pump from filter media. Return pump tees off and excess flow directed to the right of the center filter stack into refugium. Refugium then overflows into filter section before getting back to return side. Put drains in each section of sump. Drill sump for ice probe.
Hopefully the descriptions made sense and I didnt forget anything.