This has been bothering me for a few days now - the effect mass has on the hyperspace range of ships, as I can't seem to spot a consistent pattern. It might be illustrative if I post a few of the loadouts I've tried with my Cobra Mark III so you can see what I mean. All the configurations below are with full fuel loads, so that any differences in range can be more easily compared with the range of the loadout.

Setup 1:

x2 C3 Gimballed multicannons (18t)

x2 C1 Gimballed Burst Lasers (8t)

Kill Warrant Scanner (1.3t)

Point Defence System (N/A)

Military Grade Composite Bulkheads (10t)

Total loadout mass: 37.3t

Range = 7.38LY

Range with 36t of cargo (total loadout mass = 73.3t) = 5.99LY

Difference = 1.39LY

Setup 2:

x2 C3 Gimballed multicannons (18t)

x2 C1 Gimballed Burst Lasers (8t)

Military Grade Composite Bulkheads (10t)

Total loadout mass: 36t

Range = 7.44LY

Range with 36t of cargo (total loadout mass = 72t) = 6.03LY

Difference = 1.41LY

Setup 3:

x2 C3 Gimballed multicannons (18t)

x2 C1 Gimballed Burst Lasers (8t)

Reinforced Alloy Bulkheads (5t)

Total loadout mass: 31t

Range = 7.45LY

Range with 36t of cargo (total loadout mass = 67t) = 6.04LY

Difference = 1.41LY

Setup 4:

x2 C3 Gimballed multicannons (18t)

x2 C1 Gimballed Burst Lasers (8t)

Lightweight Alloy Bulkheads (N/A)

Total loadout mass: 26t

Range = 7.70LY

Range with 36t of cargo (total loadout mass = 62t) = 6.20LY

Difference = 1.5LY

Setup 5:

x2 C3 Gimballed multicannons (18t)

x2 C1 Gimballed Burst Lasers (8t)

Point Defence System (N/A)

Kill Warrant Scanner (1.3t)

Lightweight Alloy Bulkheads (N/A)

Total loadout mass: 27.3t

Range = 7.53LY

Range with 36t of cargo (total loadout mass = 63.3t) = 6.33LY

Difference = 1.2LY

If you do a little bit of maths and look at the range penalty per tonne of mass, they're not consistent. You get a range penalty of 01.7LY for installing a Kill Warrant Scanner (see setups 4 & 5) if you're not carrying any cargo, but if you do have a full load, you can go 0.13LY further if you do have one! Also, if the range penalty did scale consistently with mass, you'd expect that adding 10 tonnes for military grade bulkheads would have more of a range penalty than the 0.15LY it does have if you compare setups 1 and 5...

Perhaps we can do some citizenship science and post a few comparative loadouts to see if there is some underlying pattern and logic to loadout/cargo/mass penalties to the hyperspace ranges of the different ships?