I'm happy to hear you have been reading our threads. I trust you found our forum helpful.
So, you're building an audio truck in Mexico. Very cool. I worked with Mijares in Mexico City some time ago. I recorded him solo and with various guests for a PPV event, video and CD. I had a real blast over there!
Why are you using only 20 channels? If you have a 40 channel, 3 way splitter, why not use a W4 MASS connector and make it a 52 to 56 channel splitter, 40 to 48 splits and the rest as tie lines, etc.? One of my trucks has two 250' 52 channel snakes on board. The standard system can be set up as 250' of 104 channels or 500' of 52 channels when the active splitter or mic pres are on stage.
Here is a link to a thread about long cable runs... How far do your mic cables reach...
I have to agree with Steve and Tinderarts, 500' is too long for a passive system. When using a passive splitter, I don't like to go more then 250'. 300' is the max! Many folks can hear the difference past 300' feet. Some people, like TV audio, cannot hear the difference and have used 500' with no worries.
To my ears, the high end rolls off the further you go. You can use 500' of snake without sonic problems when you place your mic pres on stage and go line level back to the truck or when using an active mic splitter like the XTA, BSS, KT, etc.
Furthermore, we don't mind bad English. You're doing a great job! Keep up the good word! Hey, some of us speak it as our first language and still cannot spell correctly.
I hope this helped