I personally would never do that. It look like the easiest way but it is not the appropriate for three reasons.
1) Silicone will not drain easily it will probably take hours. If it is like the inferno which has only one plug...
2) If you need to change viscosities, the previous leftover silicone will alter the viscosity of the new one.
3) If you are just maintaining your diff, the silicone change will do nothing, unless you take it apart and clean it properly. The silicone will be black, like slime most of the times and this thing is stuck to your spider gears. There is no way that it is going to pour out like oil. (Unless you have a kyosho TCD)
Our vehicles are not like 1:1 cars where you just take the plug off, let the oil drain, fill it up and you 're back on the road again.
On the other hand if you re bored to take it apart, dont bother changing the silicone.
This is just my opinion on the matter, I just wouldnt do it in a competition vehicle.
Kyosho Evolva M3 / Kyosho Lazer ZX-5 SP / Xray T3