Advice on removing support from difficult areas?

I'm having trouble removing the support cleanly.

I printed a B4 lens mount, but the support inside the slot that holds the mount flange is really difficult to get out smoothly.

The first photo shows how it came out after removing with an x-acto knife, the second shows what the support looks like before removal.

Any advice? Is there a way to get the support to come away easier?

I printed this in Z-ABS, "lite" support, with 0.29mm/layer.

Source files are attached (the .ZIP has the source Python file and output OpenSCAD file).

I always find using support lite is harder to remove hence i dont use it. But that is a very small crevice 

Difficult... you could design in your own support like a single width wall on the outside that would be easier to cut out afterwards. 

Cheap, fine-bladed wooden-handled hobby carving chisels. The trick is that you want them cheap because you're only going to use the straight-bladed one, but not too cheap because if they're too cheap they're dangerous, as the Chinesium blades will fall out of the handle. I bought one set that was great and another one I had to throw away, it was so bad. Hit or miss.

Another key tool is a pair of crappy orange-handled diagonal cutters. You're not going to use them as cutters, you're going to use them to grab and twist. The Miaolisi 2501 is the best, as it has longer jaws than most, but others can be used. The higher-quality, short-bladed blue handled ones from Zortrax are not very good for support removal.

Also, you want some dental picks. Not "home" dental picks, but actual professional dental picks as used by dentists and hygenists. I have a friend who repairs dental equipment and occasionally he brings me a bucket of used scrap picks. You will break them (and it's a good idea to be wearing glasses when they do break), so you need a bunch of them.

Finally, a "bench hook" like this one make a surprising difference and can also help prevent loss of blood and body parts.

Oh, and most importantly, you need patience. Take your time. If you get stuck, work on another area - when you come back to the problem area you might find it pops right out.