[Nonfractal]

All good tips from TAMAR above  
Magnet or weight? Doesn't matter, I recommend you dump it. 
Cover the aperture with tape if the hole offends your sense of aesthetics.

Weght in analog cars ? I can put that down to personal preference.
In Oxigen cars, weight is the enemy. Tune your car by chassis & suspension adjustment etc. 
Weight and drag put load on the chip. Do anything and everything you can do reduce drag and weight. 

I guarantee that when you first do a DiSCA event, you will be aghast how much faster everyone else is using the same motors and same chips. 
There is no silver bullet. That speed comes from a  thousand cuts, every little innovation brings a little improvement in the arms race.

The best place for the flylead LED is right behind the guide, ahead of the chip. 
Drill the chassis if you have to) but never allow an LED to protrude below the chass is line. If and LED is exposed to the track and gets lens damage it will cease to work effectively. I have found that the flylead LED (in addition to the onboard chip LED) improves lane change response but I'm not sure why that would be.

Shrink wrap does take quite a lot of heat to contract it. I use a soldering iron.
Choose a wrap tube only just large enough to slip over the component you wish to protect. It does not shrink very much. 
Boxes of different size wrap tubes are available on ebay.
Be very careful when using shrink wrap close to the chip. Heat will fry it.
Dirt, vibration, short circuits, impact and heat will all mess up the chip.

If you are not going to use the hall sensor right away on oxigen, store it safely. The sensor is very fragile and does not tolerate being fitted, removed and refitted easily, especially the C-chip ribbon. You may end up changing the chassis during your tuning.

I forgot to mention, drill into the body, interior (and even windscreen if needed) to allow the antenna to protrude through. Dont bend the antenna!


Alan