I got Challenge 29-38c latex tubes from Universal Cycles last year. Use them in Challenge Gravel 120 tpi 38c race tires, very good results, light supple ride, very light. Bypasses all the sealant issues. Run low psi 35-40. Only one flat, was my fault, patched it, still good.
What size are the Bon Jons?
Edit...UC showing 19-28 in stock.
The Bon Jon's are nominally 35mm, but depending of the rim width, they actually measure around 38 mm. Thanks for the info. I'm still looking around for a place online to get them at a reasonable price. Several sites like Biketires direct list them in their catalog; but no one seems to have the 28-35 in stock. Because of latex stretchiness, I'm sure that they will be OK with the Bon Jon's. Great solution for me -- if I can find them. I've had a similar experience as you with Vittoria latex and 28 mm Conti 4000 IIs on pavement at around 70 PSI.