XM bulb too big?

[coralite]

I am a regular iwasaki, AB and ushio user. I decided to try out some of the 400w 10K xm bulbs. I noticed these bulbs are not only an inch longer but the inner light producing envelope is significantly off center with my standard 400W reflector. This is in a fully enclosed pendant so there is no way to scoot the mogul socket to lign up the inner envelope. Has anyone else noticed this? any suggestions for centering the envelope?

[gqjeff]

my xm 20k's barely fit into my reefoptix 1 reflectors.