I can't say if racks are the best way to house carpet pythons, Brazilian rainbows and boa constrictors, especially adults. I personally would use cages for adults. Racks should be fine for young animals.
You may find the below information useful.
Clay Davenport's site has a lot of useful information about rack and cage building.
http://www.arbreptiles.com/
John Hollister's site also has some helpful tips on cage and rack building.
http://www.herpo.com/
If you Google "reptile cage building" you will get the above two sites plus many others.