Ok first of all every mithral item is masterwork.
Now it would cost 7750 in order to "buy" the enchantment, meaning he gives his non magic mithral shirt to someone and he makes it a +2 shadow.
Now what DC do you mean?
Given he already has the MW Mithral shirt, the costs are as follows :
+2 Enchantment : 4000gp
Shadow : 3750gp
Total : 7750gp
So yep, you were right on that.
DC would be 5 + Highest CL of either the +2 enchantment or the Shadow.
+2 Enchantment CL is 6
Shadow CL is 5
So 5 + 6 = 11
DC of crafting check is 11 (assuming it's being done by a caster with the right spells and prerequisites).
If the caster doesn't have the spell, it's +5 DC, or 16.
If the character doing it is using Master Craftsman feat, the DC is still 16. However, remember he get's a +2 to craft it from the feat.
If he is making it cooperatively, then he does not have to supply the magic himself, so long as whoever is assisting has it. So in this case the DC would not go up.
You can also Take 10 when crafting, so if your pluses and the 10 from the Take 10 equal or exceed the DC, then you cannot fail. Just simply figure out how long it will take to make, pay the gold cost, and when that amount of time has passed you will have your item.
If he is the one doing the enchantement then the cost is halved, it would be 2000+1875=3875.
Oh and he must be at least caster level 6(for the +2 enchantement bonus).
He is having it made by a Wizard that has the magic spells to enchant the item. Thanks for all of the help and with the DC being that low(I thought it would be higher), he cannot fail. So, the time it would take to make is roughly 101 weeks:
DC 16 * (10(Take 10) + 14(Craft:Armor)) = 384
3875 * 10 = 38750 sp
38750 / 384 = 100.911 weeksThat is just shy of 2 years of time.
Whoa, there. "Enhancing a weapon, suit of armor, or shield takes 1 day for each 1,000 gp in the price of its magical features." Core Rulebook, pg. 120: The Craft Magic Arms and Armor feat.
Right, creating the armor from scratch and then enchanting it would require that amount of time, but if your GM lets you buy the base armor already made, then it would only take the time needed to enchant it.
DC 16 * (10(Take 10) + 14(Craft:Armor)) = 384
3875 * 10 = 38750 sp
38750 / 384 = 100.911 weeks
the only thing i have to say in this even thro take 10+14 is 24 sometime taking 10 dont pass the dc need to make the item
no 1100 to make a Mithral Shirt
and 7750gp it would be 8 days to Enhanct idk if you have to make the dc check eash day or at the end of 8 days. o if a player doing this its half the cast for Enhancing the armor but it stall takes 8 days
IIRC you make the roll at the end of the enhancing proccess.