Two units per Imperial Macedonian Pike Blocks without 3rd rank unit supports. I based my units differently from the Impetvs rules set mounting system guide for 15mm.
The bases are actually for 2/5mm to 10/12mm miniatures. Frontage 60mm x 30mm for Infantry/FP/FL, 60mm x 20mm for skirmish infantry S and 60mm x 40mm for cavalry/CP/CM/CL/elephants,chariots and artillery. These are actually half frontages from the 25mm/28mm mounting/basing system. The 15's do fit nicely on half 25's frontages. This way of basing, for me anyway, allows more units placed on the table top battle field playing areas. I think 8cm frontage per 15mm unit is to big if one is to field 400-600 points army. But... ;) one can still use 8cm frontage for his/her 8-10 unit Army to play with Basic Impetvs rules. mind you I don't have a problem with my opponent, :) I play solo. I live at an area where there are no war gamers within the sight of my Light Horse recon duties :o)