E5 drift, alternate insert/delete after 20000 random inserts, free-at-empty, seed 5
 cap   ops/N0  leafutil    leaves     frees/1k
   8       25    0.4610      5423      11.5760
   8      100    0.4604      5430      13.2320
   8      400    0.4604      5430      13.3327
   8     1600    0.4618      5414      13.3447
   8     6400    0.4611      5422      13.3385
  32       25    0.4484      1394       0.0060
  32      100    0.4012      1558       0.0120
  32      400    0.3754      1665       0.0280
  32     1600    0.3644      1715       0.0251
  32     6400    0.3619      1727       0.0209
 128       25    0.5809       269       0.0000
 128      100    0.5425       288       0.0000
 128      400    0.5090       307       0.0000
 128     1600    0.4852       322       0.0000
 128     6400    0.4623       338       0.0000