Attending the Toledo round of the UF1 MIDWEST series a couple months ago, I had not been to the track for some time. Unfortunately for me, my car was pretty much junk at the race and there seemed to be little I could do about it. Disgusted, I decided to rebuild the car completely, similar to the top 2 cars, which were F104W GP cars. My WGP was just not really very good.
Both guys ran the short pack, one with the battery forward, one battery back. As in the past, I have been a big advocate of the full sized battery. I did want to try the short pack since it was so good in these other cars, and I wanted see if that was the difference. In my mind, I have no problem changing my opinion or being wrong if it results in going faster!
I did initially place the electronics so I could use both types of packs. I have tried both types of packs back to back many times and have gone to the big pack almost every time. One difference is my home track replacing the carpet with the CRC carpet from this past year's IIC race in Vegas. This significantly improved grip levels at the track. In the past, there was a big difference in how the cars behaved at my track and races elsewhere due to the differences in the carpet. With the new carpet, I found the short pack to be very good, and I chose to stick with it. At the first UF1 MIDWEST race of the year in Cleveland, I actually went to the short pack and then reverted to the full sized pack and went faster. However, this was with the SpeedPassion SP-1 link car and not a T bar car like the WGP. Maybe the T bar car makes a little more grip naturally? I'm not exactly sure. Either way, I stuck with the short battery.
I can say this certainly did work well for me, as I was able to tq and win the UF1 round at my home track, as well as the Tamiya TCS race shortly after. I tried the big pack during practice for the TCS race, but as the car was set up, it wanted to over rotate.
The short pack certainly has it's place. It's a setup option as much as any other adjustment on the car. The full sized pack is definitely useful in low traction situations, and on asphalt, as I still think it plants the car better and slides the rear tires less. That can be a big difference keeping the rears from going off, especially on a hot day.