in looking at how syscalls are implemented, i see that you've picked a base of 
4096.  so syscall numbers [0...4096) are for x86_64 and [4096...-1) are for 
x32.  this 4096 limit is a bit low isnt it ?  seems like the best bet would be 
to bisect the available space for each new ABI ...

ARM EABI picked 0x900000 for their base when adding a new ABI ...
-mike