T-4

Altered flight control system based on SI-6T-2 modifications
F404-GE-402 engine
Removed drag chute
Rearranged internal tanks
Altered canards

T-3

Fixed staging issues
Disabled drag chute auto-deployment
Lengthened fuselage, added conformal gear mounting points
Enlarged wing
Moved intakes to side-mounted configuration
Moved canards to close-coupled configuration on intakes, increased area

T-2

Increased internal fuel capacity to 5,900 litres
Added wing-mounted hardpoints and stations
Redesigned vertical stabiliser
Repositioned main gear

T-1

Initial design