Sort of Partial?

Didn't really know how to search for this, sorry if it has been asked.

I'm doing the AHS SN Celebration clone, but I want 10 gals. I can't fit all the grains in my tun, so I thought up a great plan of doing half (5 gal) in all grain, (5g) half in extract and boiling them together. Plan seems pretty simple, catch is I don't know what to do with specialty grains from the extract recipe.

I was pondering just adding them to the AG side and compensation with the calculated water addition. Seems like a very simple answer and stupid question but some re-affirmation would be nice.

Thanks.

I use a 10gal rubbermaid cooler and sometimes I can't fit in enough grains to make larger O.G. beers. What I do in that case is just get all of my specialty grains and as much base grain as I can (about 24lbs total) into the cooler and then I just add DME to the boil to get the gravity where I want it.

^^ this. just mash as much as you can, sparge up to your preboil volume, and add DME to make up the gravity difference. don't forget that DME adds volume, so depending on how much you need you might have to factor that in (I messed this up countless times when I was doing partial mash brews).

Awesome, thank you!