correct flat head or oval

[yip]

 which is correct flat head screws or oval head for a patch box? and what size, i've got # 4 and 6s

[FALout]

You should look at photos of rifles from the school/area you may be copying from.  Some used only one type, others varied.  You will need to decide for yourself on what looks right for your project.

[rich pierce]

Use our library.  For example this Peter Berry has nice oval heads.
http://americanlongrifles.org/forum/index.php?topic=20788.0

[Mark Elliott]

I usually file mine flush and then back them out and slightly dome the screws just enough to knock the sharp edges off the head.   That said, if you are copying a particular gun, you should copy the screws.