When I up grade to the Jupiter caps on my X-over, Danny recommended still using the Platinum by pass caps.
I'd only bypass with another cap made of copper, if I was going to do that. IME there are sometimes tradeoffs with a bypass cap in a speaker circuit, so best thing is try it and see if you like it. Here's my general take - if you have a tin foil or aluminum foil main cap (pretty much all film caps are either tin or aluminum), then bypassing with a higher quality small cap can get you improvements in speed, detail and even tone. But, going with a higher quality main cap (like Danny's new caps or the Jupiters), you already have top-line speed, detail, and tone, plus you end up with slightly better coherence. Well, that's based on some past caps, I've not actually tried it on the 10uf or 15uf Jupiters.
I will say this, if I were to bypass, it'd be with another Jupiter or GR Research copper or Duelund cap at a .1uf value. If someone "really" wanted to use a bypass cap with teflon, I'd rec using the V-Cap copper/teflon .1uf from VH Audio. IME, teflon gives you more detail but less tone vs. the other copper caps.