I ran 1" keyed shaft axles for years on my BP. Only time I had any problem was when somebody would slam into me.
1 of my MiniPro machines has 1" the other has 11/4" aluminum. No problem with either. The 3rd one has a 11/4" steel kart axle.
TEAM580 Limited Mods (super mod, stock engine) both have 11/4" kart axles with just 2 bearings. No problems.
Both ModXRs have 11/4" kart axles.
And we lots of races, I think around 40 this year counting National events.
Tom