Measured the same way eg centre to top then the two 17inch seat posts will be the same length. However due to the larger wheels the 29er will have a higher (bigger) standover height. The top tube lengths may well be different depending on the design of the frame.
So a 17inch 26er and a 17inch 29er fit differently but will have the same length seat post.
So a 17inch 26er and a 17inch 29er fit differently but will have the same length seat post.
