OK, finally got around to stirring this one up.
Used Maris as the base grain, cut back 1# as you recommended. No Magnum was available, so I used Columbus. IBU's were higher but I cut back the Columbus addition to .4 oz to stay within style. Mashed at 154 as you did, which is a little high for me, I usually mash everything 150-152. Achieved horrible efficiency compared to recent batches; OG was 1.054.
Pitched a pretty old Pacman smack pack(six months past date), but fermentation was active ~8 hrs later. Hopefully I can wash it and save it.
I loved the color of the wort, a nice golden brown. All signs point this one being a winner. I'll post pics in a month or so(maybe sooner if I keg it). Do you have any pics of yours? It would be cool to compare.
EDIT 6/9 - Hydro sample taking while bottling was rad. Gonna be a good 'un.