With extra slotting -
certainly possible (-3.3/-3.1). But if suspension gets heavy hits, imho bolt may slip there, getting alignment out of whack.
I've heard though advices that using
paint/
fingernail paint or blue loctite/or
epoxy in place, while sounds hack-ish, may help prevent slipping. Otherwise recall reading to NOT use camberbolts in slotted holes. Though then again, why not use full strength bolt in eg. upper slotted hole, and then adjust with just one camberbolt in lower, non slotted?
Ideally one should weld on one side extra material/
washer (above simple DIY skills/tooling needed), or use inserts similar to
these (often used in rally coilovers (thus should be proven to hold up to heavy abuse) coilovers to get fixed amount of offset in slots (should come with different hole offsets) - you keep both reliability & adjustability.
P.S.
If you mentioned to be able to order customized .. why not ask instead of slotted to drill hole excentric to stock location in first place?