Years ago we used to modify alot of these 7Class Singers,we would take all the parts off the needle bar end,put the head in a band saw & cut off approx 3/8" off the lower part of it(so the feet & needle can clear).Then braze in part of the slot(at the bottom) in the lifter handle bracket so it can lift up more & we could get 1" real easy,THEN you have to find a longer needle to be able to sew the thickness.We used to use the 1000H,which I've heard is getting hard to find & is not available in a leather point.There's also a 1001 that is long you might be able to find.
I just checked & found some 1001D(Diamond point)in a size 280 & some 100H in a size 230
the 1000H measures 33/8" long & the 1001 is 31/2".
Let me know if you have any questions.
Bob