Short roll cage?

i am building my first race car and i have a used cage in great shape but i think it is to short i might not be able to see over the steering wheel. ( i havent actully put it in the car, just used a tape measure) my question is can i weld about 3 inches to the posts to raise it to the right height? im thinking of adding a small piece inside to reinforce the tube. can i do this or scrap the whole thing and kiss that money away.