It appears that the RS3-91 Does Away from the long M series Crank & needle bearing rear hsg? The GPX is the only New 91 engine that retains the long Crank shaft & the Needle bearing support rear hsg. Tony is saying 2/3 weeks before he has both new engines.
1st gen would be a Standard, Then the Ultralight, then Xtreme, & Current Kit is Stealth. The height of the sides of the boat & the width changes thru all of them. The newier current Kits are Higher on the Sides & Narrower width.
No one mentioned Servo Muscle or the battery Voltage or the C rating on Battery or linkage size or deflection,. For turning HARD Right. There are mechanical advantages all over the boat, Inside the radio box & out!! a 18-20 lb Twin Hydro running over 90mph will make you seek every advantage...