Yes, that'll give a bit more depth (ie it's the inline series resistance I was talking about - as the LDR decreases in value, the pickup's load will increase, as will the current, therefore you get a more of a signal voltage swing), but a 5K pot as the top resistor of a two resistor divider chain - ie where the bottom resistor is the LDR - isn't likely going to have a huge amount of effect (though this will depend hugely on the 'light resistance' of the LDR and how efficiently the LED is optically coupled to it) - making the pot larger in resistance will have more impact, but then you lose signal level.....