Reservation on JR before getting railpas

Hi,
I am sure the question has been asked before but i could not find an answer.

We are planning a trip to Japan in the busy holliday period (end april/begin may) and we like an advanced reservation on the bullit train using the JR railpass. The first travelling day is also the day we want the railpass to start. The problem is that according to the Railpass site you have to show the railpass when you make the reservation (so you already have the voucher exchanged for the actual pass). And you can not exchange the voucher ahead of time. Let alone make a internet reservation in advance. Baisically this all means that in our situation we can only make the reservation a littlebit ahead of time (1 hours or so) if there are still seats availble. This does not give us the peace of mind to be sure we can make the trip and have a seat in the train. Is there anyway around this?
B. Slager

Reservations for the Tohoku, Akita, Yamagata, Joetsu and Nagano Shinkansen can be made online in advance (even before you purchased the rail pass):
http://jreast-shinkansen-reservation.eki-net.com/

But reservations for the Tokaido, Sanyo and Kyushu Shinkansen are not possible until you arrive in Japan.

The Tokaido Shinkansen runs between Tokyo, Nagoya, Kyoto and Osaka:
http://www.japan-guide.com/e/e2018.html

Thanks for the response Uji.
I guess the one JR is not the other JR.
B. Slager