Tactics for reaching full attenuation?

I wouldnt go any warmer than you are now. Are you pitching enough yeast and shaking or oxygenating your wort?

 

Pure oxygen can help some but I don't think that is your problem based on what you are already doing. What do the recipes that are finishing high look like? Too much crystal malt can cause a high fg. Also are you using extract or all grain?

 

That is a reasonable amount of crystal. Make sure that you have an accurate thermometer and try mashing a little lower (150 would be a good starting point)

 

That sounds like a lot of crystal to me. I'd try cutting it in half, just as an experiment.

 

OK, need to butt in.

If you are making a 5 gallon batch with 16 lbs of 2-row and 1 lb of crystal, at 75% efficiency your OG is 1.092. How close is this?

Being that you are at 1.016, your attenuation is at 82-83%, not bad. That's 9.9% abv though. Typically, DIPAs have an FG from 1.012 to 1.020. You are dead center. How low do you want the beer?

This is already a pretty light DIPA in terms of color. Removing crystal will make it even lighter. A DIPA with no malt character will just be a hop/bitter bomb. Maybe this is what you are going for? But, it is usually okay for a 10% DIPA to have some malt character.

If you really want to lower your FG - lower your OG. OR - replace some of your base malt with sugar. If you take out crystal - add less of a darker crystal to give it some color and body, and a bit of a backbone. The less crystal you have, the drier the beer will be, even if you match the color with a darker crystal. Of course, you can combine these tricks as well.

Finally, I don't think this is your problem - but pitch more yeast. You should be striving for about 280 billion cells by my calcs. If your 10% beer is a bit hot, this will help.

Good luck!