So, has your customer agreed to GMAW Spray? Or, are you trying to get their acceptance? Post all the details (position, materials, size/thickness..etc) and help will follow.
Spray will work well for cover and fill passes, but only if the welds are made in a positioner and rotated for a constant flat position.
If you need to work out of position, you could try spray/pulse transfer.
Also, Lincoln's STT (Surface Tension Transfer)or Miller's RMD (Regulated Metal Deposition) transfer is a new improvement to short circuiting, specifically intended for a more efficient GMAW replacement for GTAW open root welds.
If it were me I'd STT or RMD the root and pulse the rest.
90/10 works.
You might want to try 98/2 (2 is oxy). It helps the bead wet in on the toes very well.
Metalcore wire is another option. It runs like butter, nice and smooth.
I suggest letting your welders play with the options, pick a winner, qualify your procedures, and then go make money.
Tim