Return to basics. The fan (clutch) is controlled by the thermostat, or more accurately, the temperature of the coolant (air) passing through the radiator. If the fan is engaging later than you like, you will need to adjust the thermostat, or its control (if it's electronic, as are some late models). Electronic controlled thermostats are adjustable with programming, or calibration updates. If it's a traditional thermostatic controlled thermostat (mechanical), replace them with stats that operate in the range you want/need. If it's still not aggressive enough for your needs, more aggressive fan clutches may be available, or mods to your model may be an option.

Another option is to reinvent the wheel. Toss the old technology and rethink it. Evan's NPG is another route to healthy engine temperature control. Simply, don't worry about it. NPG (Non-aqueous Propylene Glycol) is an engine coolant that doesn't boil, and operates normally at zero pressure. It contains no water, so no boil. It moves the heat out of the engine without the need for a pressurized system. I've not experimented with it myself (and I have no vested interest in it), but the principal is solid. It costs a bit more than traditional coolant, but it's non-toxic, and offers a benefit to the cooling system, in that it, operates at no pressure. Seals, clamps and components simply don't leak, as they can under traditional conditions. I've heard plenty of skeptical reviews of it, but no anecdotal complaints of performance or failure. It has drawbacks, but an otherwise healthy system will integrate it well.