Cylinder wall thickness: what is too thin??

I have this block I machined in auto school, era 1978-ish 360 block, .040" over. I have ALL the parts ready to be assembled, including 40-over pistons. Upon testing the block, I found a spot midway down on the 6th cylinder which has a thickness of .088". :banghead: :oops:

I have heard never use a block with a cyl thinner than .090". I dont know what to do, since I already have the pistons which cant be returned. Should I build it and run it as-is, since the spot is midway down on the cyl, or should I have the block sleeved... what do the pros think??