I cannot imagine keeping a litter of puppies in a 4x6 box until 8 weeks. No wonder you had chewed corners. Mine are out in a bigger area -- 10x 12, in the same room by the times they are able to crawl over to the edge of the box. My Durawhelp has lasted for 13 years and about 15 litters but as I said, they are out of there and exploring and playing by around 3 weeks.

I got the two 4x5's using the second 4 x 5 after 3 weeks, attaching it with no door from one to the other. It's a dream! One is more for potty & feeding, the other for sleep and play. The pups can go back and forth at will. Even a litter of 11 and 12 do fine with two 4 x 5 footers. They also make gray fleece with Velcro or Zinfndel sells better fleece cut to order.

I would go Durawhelp or Jonart. A huge price difference but anything in between is just that. Durawhelp for the price and easy, lightweight storage is the best for the buck. Jonart is great but 2 1/2 times the cost and clumsier. If used often, leave it up. Otherwise the Durawhelp gets cleaned and back in the box, easy peasy. I get 7 to 8 litters in 6 years out of each Durawhelp, not a bad deal at all. There are now top corners available to be purchased to reinforce the box, not necessary but nice to have. If money is an objective, go Durawhelp. I never heard of the other Hearts box and I'm breeding for going on 3 decades.