While we're on this, why can Experimentals and RAAus not equip with non-TSO'd GPS' like the Dynon -2020 and the Garmin -20A that provide better performance than a Garmin 430?
The US approves it, and they're the damn country that invented the TSO's. The UK has recommended such an approach there too, but here we have to have a GNS-430W at better than $10K or a Trig TN70 for well over $3K