mustangace,
i have a webra .61 speed in mine...flew it again today...you will be just fine, probably happier if you did go 60 size power. we have 4 us40's in our club...50 size power with tuned pipes is the lowest power flown. others include mds 68, webra 61, thunder tiger 61 etc....the 60 size power is by far the favorite choice. just my $0.02...later

chris