Can I do this?

I always thought internal dialogue was first person because it is dialogue, just with themselves. Although some thoughts can be narrator originated, though they are the characters feelings or thoughts, of which would be third person. such as, "Daniel knew that there was no way that he would ever move in that direction unless the powers that be forced him to." or "I'll never move in that direction unless the corporation leaves me no choice."

Hi Kiwi.

This is a good question. I also do this occasionally in my WIP, too. Sometimes the impact seems to be more powerful when I use 3rd person for the MC's internal feelings or dialogue. I also use first person reflections within the same WIP, although I try to keep both methods to a minimum, using either only when my MC feels very strongly about something or is being severely affected by what's going on. I feel less use ensures maximum impact.

I find that doing this helps me cut out the he knew/he felt/he thought 3rd person traps, especially in parts where there is a good amount of heavy internalization for the MC.

I'm not sure if this is an "accepted" way to do things. I always thought that if you write in 3rd person limited it's understood by the reader that they are bound to only that character's perspective, no matter what you are trying to convey. In my opinion, if it's alright to report observations directly, it should be ok for thoughts, too. Just like you don't have to use "he saw" everytime your MC looks at something, I see no reason why you should be forced to use "he knew/thought/felt" either. If you describe an object, the reader should know it's through your MC's eyes. If you write a thought, they should know it's from his/her mind.

Just my take on this. I never really thought about it much before. It'll be interesting to see what others have to offer.

Charlie

Kiwi, you're doing it right. And yes, use both methods. You can also use thought tags, but then don't use italics.