Confusion about positional tolerance for rectangular pins

[dulman123]

Hi I'm a new user of GD&T and recently I got confused about a partner's drawing and I would like to propose some change.
However, I got no confidence about my proposed change.
I googled a lot about positional tolerance trying to find some explanation of similar case.
But, all the posts explained positions of cylindrical holes and use surface as datum A, B, C.
I rarely see the introduction about the positional tolerance for the mid-plane of a square or rectangular hole/rectangular blocks.

I put a few question in the attachment, appreciate if anyone could help clarify and explain them.

Thanks a lot!

 

[rb1957]

IDK much about GD&T but I suspect it doesn't like mid-planes as a datum (maybe because it is hard to define, as opposed to a surface). I'd ask this of someone where you work, who may also direct you towards texts and such when you show an interest in your work. I would also not be shy in asking around "why not this ?" ... if they pick on you for showing "ignorance" then you've learnt something about the office.

 

[mfgenggear]

oP
True position for round holes or pins is insure assembly of details. if there is more than two details. then it can be matched drilled.

a rectangular hole could apply if it requires assembly.to an other details.
and the reason for rfs (regardless of feature size and MMC (maximum material condition) and more.
what to keep in mind precise very precision tolerance requires very expensive manufacturing cost. so make sure it really is required.