I understand that you're racing within what defines the class. with Mabuchi 540's and 1500's....was that class not designed and put in place to be a low cost spec class??
running that gear in the latest high-dollar cutting edge chassis..isn't that almost contrary to what the class was put in place for?
is your stick pack a true stick pack? or is it a side by side pack?
Xray gives you the option of adding either type of mount..although, as has been previously stated, going to all the cells on one side will take your perfectly balanced car and bias it to one side...forcing you to add weight to again achieve balance.
I stayed away from saddles too...even bought a CRC Carpet knife 12th scale so that I could avoid 4 cell saddle packs....
I then found a great deal on a used Xray T1 and have had no problems with Saddles..the battery retention strap system works wella nd secures everything in place with little hassle...and with a careful placement of the bridge wire you can still use the saddle packs in-line as a side by side pack.
if your old Tamiya kits require a true stick though....possibly keep a couple of sticks assembled for them?
You're looking at spending hundreds of dollars on a new pro-level touring car and you're going to let the decision be made by battery ypacks that sell for a few dollars each??
The decision is yours to make.....good luck