I do have one now. It came with the tank. I bought both tank and fuge used. It is a 20 gallon tank with baffles put in. The ones I have seen on Amazon are from a company called Wind Rider Creations.Do you have a sump / refugium now? In my opinion you'd want at minimum 40 gallons for sump. You can divide the space how ever you like. I have 29 gallon on 125 about 1/3 is the fuge it would be bigger but I couldn't fit a bigger sump in my stand. I think space is the limiting factor in the large end.
What type of DIY kits are you looking at?
Sorry this is long in coming. Not sure how the PM process works. I would love to take a look at those instructions. How do I PM you?You mean assemble it in the stand? I really doubt it. you need full access to all sides. If you want to PM me your email address I can try to email you his instruction book and you can read through it as see if it looks like something that you want to try.