That's good to hear Greg - it is around my neck of the woods, which, as you indicate, don't tend to be run in/around as much as other parts of Snowdonia! I've known Henry's family for over 20 years and I knew he would put on a good event given his passion for the area and ultra running. Unfortunately I wasn't able to help out (other than spread the word) given I was organising my village race (down/up the Conwy Valley).
Ali - I agree with Jason re the plan. I can't see the logic of running quicker than marathon pace in a long run and to do that in the 1st half just seems bonkers - no wonder you feel tired in the 2nd half. My 2p would be to throw some target marathon pace miles in the 2nd half of every other one of your long runs, although as Jason says may be a bit late now with it being just over 6 weeks to go. I've done quite a few Snowdonia's off 35miles pw and whilst the lack of miles has kicked in in the last 6 miles of a couple of them I wouldn't say to a marathoner that you can't run a marathon well off that kind of mileage - you've just got to make sure they are the right type of runs rather than running the same kind of pace for each of them. My 2p is that one of the 4 runs has to be a long one (with some quicker stuff thrown in) and 2 of the other 3 should have some quality in them - a mixture of fartlek, hills & intervals.
Massive - I have to disagree with the advice that you should not be running over 20miles, although it does depend on what pace you are running at - clearly if you are running it at target marathon pace then you are going to increase the risk of injury. In my opinion time on feet is as important as the miles - I always start my long runs at least 1 minute quicker than target marathon pace (quite often mara pace +1m15-1m30s) before picking up the pace after a few miles - as mentioned above I will throw in some miles at target marathon pace in the 2nd half of my long runs. Also, with Snowdonia I try and mimic the race profile by throwing in the hills, where I will put in a bit of extra effort on the climbs, then recover on the descents.
brer - good look with this weekends 2 marathons - if you do ever decide to put together details of your marathons, with your thoughts of the various events, courses, organisation, atmosphere, toughness etc perhaps best not mimic trex otherwise it will be like War & Peace!?
brer - that has to be all marathon runners worst nightmares - the fact that you were not able to resolve the issue straight after the race must have made it worse!? I shouldn't laugh, but.... Congrats on another top finish - I don't know how you keep on churning them out (the marathons/podium finishes that is!). How many is that now? I am sure you do more marathons in 6 months than I've done in 8 years - since 2007, I'm up to 15, with 7 Snowdonia's - thus next month half of the marathons I'd have done would have been Snowdonias!! You should pull together a marathon guide, giving your thoughts on all the marathons which you have done to date!?
Just a heads up for a cracking 30k race, which is taking place on Sunday October 5th (start time 10.30 I think) and is great prep for Snowdonia, particularly given that it includes the section between Rhyd Du and Waunfawr and has some decent climbs! It's called the Four Lakes race and it starts & finishes in Rhosgadfan (not far from Caernarfon)