yeah, been playing with the sdk the last couple of days I managed to make my diracLE~ object into a cross-version external that uses 64 bit in max 6 and 32 bit in max 5 that was quite a puzzle, but it works now. (I will upload it later today)

the 32bit version works fine in max6 btw, though you have some overhead (and less precision of course), from the 6.0sdk:

"This means that the 64-bit engine will work just fine with the older 32-bit objects. - However, the conversion comes with some computational expense. For the best per- formance your objects should support the 64-bit dsp chain natively by implementing the "dsp64" message as explained below."

beta SDK? where can I find it?

here: https://cycling74.com/download/MaxSDK-6.0.0-prelim2.zip