Hi Iain,
Personally I do not use the Comparadun style of fly and am not sure if any of my friends do either. Having said that they will work well just like many other styles. Your top fly looks really good and though you have just 2 Microfibbets,they are long so should support the fly well. This length of Microfibbet tail may not be so good for Grayling but that aint a problem in Aberdeenshire!!
Most of my dries are either Parachute/Paraduns,F Flys and Klinkhamer types with quite a few foam jobs for terrestrials and collar hackles for very small midge(24 or less). I even use parachutes for spent spinners sometimes with a fluo yellow wing post that shows up well in the fading light,a couple of turns of hackle and a bent shank(a la Stuart Crofts). Many times I have fished this to the point where the parachute hackle has come off after catching umpteen fish and I have for reasons of fading light,lack of time or laziness continued to fish with the fly which will be kept up just by the floating qualities of the wingpost and it has been just as effective.
I always use Poly Yarn wings on my duns and prefer it to Deer Hair(which I use on Caddis). All my Don duns have either natural Poly Yarn colour wings,pink,yellow,white or black (great for 'shiny/glassy' water-GOOD TIP!!). I do not find that the colour puts the Trout off and it IS important that you can see where your fly is if at all possible.
Used to use Microfibbets till a few years ago and mostly use 6-8 Coq de Leon fibres which retain their shape after hundreds of casts but are not too stiff.
Must ties...not really. I went overboard years ago in preparation for our trips to the Don and have at least 2 'Don boxes' full of dries and spiders to match the Spring hatches/falls we have encountered i.e MB,IBD,LDO,Olive Uprights,Beetles,Black Gnats,Terrestrials. One thing about the Don is you do not lose flies in trees as there are not many about,and the type of fishing we do is targeting big Trout so we are not catching many fish and by fishing mostly 4X or 5X tippets we have never been broken off. So our flies tend to last a long time and sort of don't need replacing!
I am going to tie the parachute and emerger Grannom patterns which were in this months T & S (the same patterns were in FF & FT last Spring) only because I hit a good hatch May 3rd last year with plenty of rising Trout and I persevered with an F Fly pattern even though I could see that they were not taking the adults(doh!!) and subsequently blanked. I reckon if I had on one of the emerger patterns I could have had good sport. So I will be tying up 6 of each.
I guess you must have good Grannom hatches further down on the Don? We would love to hit a good reliable hatch but think that Monymusk and above where we do most of our fishing may be near the top end of the where they emerge as they are not really an upper reaches fly. Do the Trout further down respond well to them?
I have quite a few with trailing shucks of poly yarn including LDO,Iron Blues and March Browns for the Don and find they work well.
Richard