Front subframe lower arm bracket cracked!!!

[5even7]

I recently had to replace my 115000 mile 2007 base 2.7 Caman front lower suspension arms and have run into a problem with the front subframe mounting brackets. I managed to remove the the seized old bolts with an angle grinder with no damage to the mounting brackets (not easy) but on trying to torque the first inner arm bolt up (120nm / 89 lb ft) the subframe bracket cracked on the rearmost nut end (new bolts and nuts used). I've managed to tig weld the crack for the moment but haven't dared torque either side up. A new subframe is £780 with some good discount from my friend at my local Porsche centre but I'm reluctant to make the purchase if I'm likely to destroy a brand new subframe. Anyone else had this problem & are my torque figures correct?