Not sure if that would do you any good Nath , cos if you have not got the sun in the first place then another MPPT will do you no good , it cant convert what isnt coming in , neither will 2 of them .
Instead of spending £60 on another MPPT to give you 25% extra off whatever is coming , i would be more inclined to add another £5 and get the 30w poly panel they do , that can bring in 1.71 amp peak , which is more than an extra MPPT will gain .
Wire all the panels in parralell and then to watt meter , then to MPPT , then to other watt meter , then to battery .
Dont take that as gospel , but i reckon that is the best chance of higher amps i think .
No doubt Mr Spruce will be along shortly to add his expertice to the mix