Hardcore and mean suggestion :
All 2h above the HGS (included) + war cleaver, morningstar, bar mace, great axe, mallet and great bardiche : 2.5 slots
Flamberge and great maul : 3 slots
All poleaxes + glaive, GLA, GLB, swiss halberd, english bill, long voulge, pike, long spear and long maul : 3 slots
For the other polearms : length < 150 => 2 slots, others 2.5 slots
1h : all 1 slot except if length<95 and weight<2, then 0.5 slots.