I did a small app to benchmark extension performance of major Eiffel list data structures on my Win32 XP machine, using EiffelStudio 6.2.7.3489, Microsoft (R) 32-bit C/C++ Optimizing Compiler Version 14.00.50727.42 for 80x86, Microsoft (R) Incremental Linker Version 8.00.50727.42.
I extend [INTEGER, INTEGER] into the lists, and calculate time and memory usage (increase).