Hi Hippo,
The 100 is going to be fairly harsh so if you had a high workload already this year you might wanna stay at 50.
The loop I am designing does not have any real long climbs like you will get in US 100's, but it is going to be a rollercoaster type of affair. Some very steep, short up and downhills and lots of 'em. The aim is roundabout 1400ft of climb per loop, so 14,000ft for the total race if you do the full enchilada.
Stoney uphill struggles, lots of treeroots and other ankletwisters, some nice sandy uphills, deep rutted tank tracks.....
One thing I think is useful is to let you make your mind up as you go along, so if you feel good, feel free to keep running.
If you had enough, you can stick at 50.
Hope to see you there, follow Caesars Centurions!
Henk