Here is some verified data on weight reduction for the NA and NB Mazda MX-5. Starting with the tub weights, it's evident that the NB chassis is stiffer and more rigid than the NA. I've also included the Lotus Elise and Alfa 4C tubs to illustrate the hypothetical weight limit for a two-seater sports car chassis.

Bare NA Tub: 466 lbs (211.36 kg)

Bare NB Tub: 495 lbs (224.53 kg)

Bare Lotus Elise Tub: 150 lbs (68 kg)

Bare Alfa 4C Tub: 143 lbs (65 kg)

List of Weight Reduction Modifications:

• Air Conditioning System: 38.00 lbs (17.24 kg)

• Gutted Doors: 20.00 lbs each (9.07 kg each)

• Removable Roof: 37.00 lbs (16.78 kg)

• Seat: 33.00 lbs (14.97 kg)

• Spare Tire and Jack: 27.00 lbs (12.25 kg)

• Roof Removal: 40.6 lbs (18.41 kg)

• Window Mechanisms: 20.00 lbs (9.07 kg)

• Wiring Reduction: 15.25 lbs (6.92 kg)

• Gutted Dashboard: 8.4 lbs (3.81 kg)

• Audio Equipment: 10.75 lbs (4.88 kg)

• Replaced Lights with Fixed Units: 10.50 lbs (4.76 kg)

• Removed Power Steering: 10.00 lbs (4.54 kg)

• Bumper Modification: 10.00 lbs (4.54 kg)

• Airbag Components: 8.00 lbs (3.63 kg)

• Heating System Components: 7.00 lbs (3.18 kg)

• Lighter Flywheel: 6.00 lbs (2.72 kg)

• Lighter Exhaust Manifold: 6.00 lbs (2.72 kg)

• Trunk Lid: 6.00 lbs (2.72 kg)

• Lighter Wheels: 6.00 lbs (2.72 kg)

• Removed Emissions Component: 6.00 lbs (2.72 kg)

• Lighter Alternator: 5.00 lbs (2.27 kg)

• Wiper System: 5.50 lbs (2.49 kg)

• Firewall Insulation: 5.25 lbs (2.38 kg)

• Replaced Steering Wheel: 5.00 lbs (2.27 kg)

• Insulation Removal: 5.00 lbs (2.27 kg)

• Front Bumper Modification: 4.75 lbs (2.15 kg)

• Trunk Hinges and Catches: 4.50 lbs (2.04 kg)

• Fan and Hose Components: 4.50 lbs (2.04 kg)

• Removed Side Bar: 4.50 lbs (2.04 kg)

• Top Mechanism Components: 4.25 lbs (1.93 kg)

• Removed Audio System: 4.00 lbs (1.81 kg)

• Removed Tow Hooks: 4.00 lbs (1.81 kg)

• Carpet Insulation: 4.00 lbs (1.81 kg)

• Removed Door Components: 4.00 lbs (1.81 kg)

• Battery Swap: 4.00 lbs (1.81 kg)

• Lighter Battery: 3.5 lbs (1.59 kg)

• Seat Belt: 3.75 lbs (1.70 kg)

• Air Intake Components: 3.75 lbs (1.70 kg)

• Speaker and Antenna Wires: 3.50 lbs (1.59 kg)

• Rear Tow Hooks: 3.25 lbs (1.47 kg)

• Airbag Sensor Components: 3.00 lbs (1.36 kg)

• Trunk Structural Components: 3.00 lbs (1.36 kg)

• Window Mechanism Replacement: 2.50 lbs (1.13 kg)

• Engine Pan: 2.50 lbs (1.13 kg)

• Metal Panels: 2.50 lbs (1.13 kg)

• Washer System Components: 2.25 lbs (1.02 kg)

• Sound Deadening Material: 2.25 lbs (1.02 kg)

• Fuel Line and Battery Covers: 2.00 lbs (0.91 kg)

• Removed Door Material: 2.00 lbs (0.91 kg)

• Canister and Hoses: 1.75 lbs (0.79 kg)

• Brace Components: 1.75 lbs (0.79 kg)

• Mount Components: 1.75 lbs (0.79 kg)

• Lighter Radiator Fans: 1.50 lbs (0.68 kg)

• Removed Hood Latch Components: 1.50 lbs (0.68 kg)

• Air Ducting Components: 1.50 lbs (0.68 kg)

• Fender Liners: 1.25 lbs (0.57 kg)

• Sill Plates: 1.25 lbs (0.57 kg)

• Removed Carpet: 1.25 lbs (0.57 kg)

• Control Panel: 1.25 lbs (0.57 kg)

• Switch and Spring Components: 1.25 lbs (0.57 kg)

• Removed High Beams: 1.25 lbs (0.57 kg)

• Removed Visors: 1.00 lbs (0.45 kg)

• Rear Fender Liners: 1.00 lbs (0.45 kg)

• Removed Latches: 1.00 lbs (0.45 kg)

• Fuel Line Cover: 1.00 lbs (0.45 kg)

• Removed Deck Metal: 1.00 lbs (0.45 kg)

• Side Mirror: 0.75 lbs (0.34 kg)

• Speaker Covers: 0.75 lbs (0.34 kg)

• Radio Surround: 0.75 lbs (0.34 kg)

• Drain Tubes: 0.75 lbs (0.34 kg)

• Sunvisor: 0.75 lbs (0.34 kg)

• Door Stop: 0.75 lbs (0.34 kg)

• Gas Lid and Switch: 0.50 lbs (0.23 kg)

• Removed Valve: 0.50 lbs (0.23 kg)

• Removed Bracket: 0.50 lbs (0.23 kg)

• Fuel Filter Cover: 0.25 lbs (0.11 kg)

• Removed Switches: 0.25 lbs (0.11 kg)

• Removed Antenna Cable: 0.25 lbs (0.11 kg)

• Removed Brace: 0.25 lbs (0.11 kg)

• Removed Connector Bracket: 0.25 lbs (0.11 kg)

• Removed Hoses: 0.25 lbs (0.11 kg)

• Removed Antenna: 0.25 lbs (0.11 kg)

• Removed Lock: 0.25 lbs (0.11 kg)

The total weight savings from the modifications totals 518.55 lbs (235.31 kg). Having a clear idea on the goal of the build is key, and personally I feel it’s important to balance weight reduction with reasonable comfort and usability.