As long as it complies with; http://emra.ca/Forms/2011_EMRA_Competition_Handbook.pdf
Section 1.3
As for being on the bottom of the fairing, probably not a great idea as the lap count officials are above you on the tower; they need to see your numbers.
Those numbers on the belly pan are a suppliment to the numbers on the front fairing (facing the tower or centered) and the numbers on the tail section. The reason you are seing them on the lower fairing now is because the new tail sections are getting too small to have numbers on either side.
The 194 on the bike in the background is more clear. It only takes one time in the tower trying to read bike numbers as they go by to realize why the rulebook requirements for numbers are there. Make it as big and clear as possible.