The watermelons here (all seedless) have very thin rinds; they're quite unsuited for pickles. Do ones w/black seeds have thicker rinds?

Here is an example. The rind varied between 3/4" to 1". The thickness is overall consistent around the diameter except for a small part that has been lying on the ground during ripening. The black seeds are in the upper two thirds of the slice, so they are not visible here but this is a black seeded variety.

AJ, I don't have my grandmother's recipe, but as HLA says, she had some pink in her rind pickles. That said, I think the black seed watermelons do have a thicker rind.

An inch easily. I have one that I plan on slicing tomorrow, and will try to post a picture of the rind for you.
Maybe it's just me but I think that a good watermelon should have a thick rind to protect the good stuff inside, regardless of the fact that you end up with a lot of useless material afterwards.

That's strange because we (in virginia) have seedless watermelons with some really thick rinds great for pickling! Do you have a good pickling recipe? i'm new to jarring and pickling and tried a simple recipe for making quick and easy pickled watermelon rinds which was okay...not the best. So I'm looking for some good recipes to try out the next time I buy a watermelon. Hope you find a watermelon with a nice thick rind!

This doesn't exactly answer your question, but it may help in some way. The recipe leaves some of the pink part of the watermelon in the pickle, so you could potentially use a watermelon with less rind. http://www.portlandmonthlymag.com/eat-and-drink/articles/watermelon-pickles-0810/

I sure hope they do! Imho seedless watermelons also are relatively flavorless compared to the seeded varieties.