I finally managed to open it too.Looks great.I ordered a 1930/8 a few days ago to use in my 4.5kg LST on 4s.I was going to get a 1940 initially until i read about your savage.Thanks!
I'm using a centre diff so i was going to use a bigger motor with lower kv but then i found some 4.09:1 diffs so i reckon the 1930 should be OK with a 10/51 gearing(20.85:1 final drive ratio).