It´s ok to dremell the battery tray like this?
 

Since my packs are too tall I´m thinking of dremmeling out one full side of the RC-Monster battery tray so I can fit the packs on its side, but hey! that would left the bottom side to be only 1mm thick (as it is already) but without the extra strengh the side is giving to the tray. The packs would surely be secured with the straps but I doubt about the overall strengh of the battery tray suffering too much.

I´m not willing to buy a custom battery tray since I don´t know if this is the battery I´ll be using for a long time, but maybe that´s the only solution... Anybody tried this before?

The trays are made of machinded delrin or nylon blocks I believe, so removing one side shouldnt hurt like that. Although, whats to stop the batt from sliding out that side- another strap over of around the tray should do the trick.

Well my battery tray has already 2 straps going side to side so that wouldn´t be a problem. I´m thinking of trying this cos I´m going with the car to a nitro race this friday and sure they´ll find enough downsides on the electric cars to add the body bended to a side because of the battery...