Is it possible to use a DX1215 expansion unit with a DS1812+?

According to Synologys website, the DX1215 expansion unit is only 'supported' for use with the units that have 12 or more bays to begin with. However, is it possible to use it with a smaller box, like a DS1812+? What result would I see if I hooked a DX1215 to the expansion port of my DS1812+? If it wouldn't work at all... what exactly prevents it from working? Does the Synology software detect what model it is and explicitly block its use, or is it a more fundamental issue? I recently found out about XPEnology... any chance using that would enable me to use the larger expansion?