Big,
I use several diamitors of the the flex bits for just what u are talking about. I drill 2 haole on topplate 1 for bit 1 to look down. The 5/8" flex bit is 6' long and has a larger shank, then I make sure to get it in the middle of the cross cat. It does get tough on the old plaster walls the plaster laying on the cats destroys the bits. I try not to use the flex bit that are like the ship aguer cause you cant sharpen them they need to have the bit tapered back.
http://www.milwaukeeconnect.com/webapp/wcs/stores/servlet/product_27_40028_-1_681903_192645_192327# Hope this link works.
Ob
