Hatching Guinea Fowl Eggs

A friend tried to hatch 30 of his eggs in an incubator and none hatched. I told him that if he found any more I would give it a go, I have had quite a bit of luck with chicken eggs in my incubator purchased through the post.
Last week I was given 16 eggs, they were no more than a couple of days old, clean well shaped eggs. I let them stand, pointy end down for 24 hours just to be on the safe side,  even though they were carefully collected and i only live 5 minutes away. They will have been in the incubator 7 days tomorrow, yet all eggs seem to have candled clear!
I know they take longer to develop, is it still too soon?
There are 8 birds, and at least 2 are male and they free range round the farm, if it isnt too soon is it something we are doing wrong? Are guinea fowl eggs harder to hatch?

Thanking you in anticipation of your help!

This web site 'Guinea Fowl UK' suggests optimum temperature and humidity levels that may differ to most books.  I don't know whether this helps and it doesn't really answer your query regarding candling, unless the temperatures differ greatly which might explain why nothing has happened so far.

http://www.guinea-fowl.co.uk/07-breeding2.html

Although this web site explains that the shells are much thicker than chickens so candling is very difficult and you "might not see anything until it becomes large and obvious".

http://mymilescity.com/guinea/candling-day9.html