you have to Adapt/Improvise...it's an ongoing, perpetually flowing situation...
I think you probably could. You can take lights completely apart. NOT FOR the Timid!!!
I WOULD NOT ReCOMMEND you do this at home; Unless you know what you are doing or are Supervised by someone who does... DANGER DANGER

In answer to :question:...As long as the 400bulb isn't too much longer than the 250bulb,
It should work fine.lw :smokin: