Advice for 25-50 Mbit SPI lines - PCB design
When you have a signal with short rise time, you need to be concerned about SI analysis and termination to prevent from reflection. 

A simple rule is this: all traces longer than 0.3*Risetime(ns)*7.5(cm) need SI analysis and termination. 

25MHz is some how high for SPI communication and you could have unwanted radiated emission due to long 17 cm traces. Length matching is not the case here but adding some ground traces as guard lines could reduce the probable emission and RF immunity problems. the guard traces could also reduce the return path loop then reducing the unwanted antenna gain. The probable problems are depends on the distance between the SPI routing layer and the ground layer. the less distance, the less problem.