Dave, if you have trouble with photos becoming darker with increasing the f# then try reducing the speed. Each camera varies so much it's a matter of experimenting, I had to revise how I used settings when I changed from a Nikon D90 to the D7000. It makes a big difference according to what lens you use too.
You can only safely go down to 1/160 sec. for hand held shots but can go lower with practise. Increasing the ISO will also lighten up shots in dull conditions.
With the D90 I used +EV quite a lot, it worked for that camera but I don't use it with the D7000 as I can achieve the results using just speed, f# and occasionally ISO. If what I use works then I tend to get stuck in a rut, when checking a photo recently I looked at the full details and realised I had increased the flash setting by one stop which seems fine and I remember doing it I think in autumn when taking photos in a dullish spot. That made me think about reverting the flash to neutral setting or to a minus for summer when and if we have bright sunshine.
I always use the flash and manual shooting for insect photography, the results in manual are far superior to using auto and flash is necessary to highlight detail on very small insects. I don't use a screw on lens as I have a 2x tele-convertor attached to a prime 105mm macro lens. Using auto doesn't give anywhere near the same magnification as using manual does, and the camera can have trouble focusing on small objects in auto. The addition of a tele-convertor has the effect of making darker shots too, once you know what works for a particular set up it becomes second nature. Then the camera wears out, you have to buy a new one and the learning process starts again!
I use spot focus along with spot metering which concentrates focus and light on a small area in the centre, that also has the effect of darkening but is essential for insect photography. If I take a more distant shot it still works well on those settings if I alter the f#, and speed. I also have my lens set to 0.5M, I rarely change that for distance shots but it still works, if I change it I forget to put it back!
