i had a stick locker behind my old 4AGZE and never broke it. as long as you prep it it'll be fine. best way is to pull the crownwheel off, pin spider and side gears out and clean it well with petrol. then pre heat the centre with an oxy or stick it in the oven for a while. doing this will stop the welds from cracking as the centre absorbs the heat from the welds. you will also want to put it back in the oven once you have finished and slowly bring the heat down. this will stop it from cooling down to quickly and stop it from cracking also.
don't put bolts and crap in there, it'll just make you look like a dodgy c**t.
or you could also get the centre filled with aluminium.