There are lipo trays that will suit the 415 and locate the battery nice. I ran one for a long time, i think it was ( itty bitty design ) was the brand.
If you look at the tamiya 415 thread there are numerous pages and pics on teh subject.
I recently ran my 415 and with lower race weights now the tray was too heavy.
I removed it and just taped it in with a small weight at the fron to stop it sliding in and hitting the belt. Worked a treat.
But if you are not worried about weight, look for the lipo tray and it is teh best and neatest way of holding in the lipo
TAMIYA - SMOKEM - REEDY