+1 on the recommendation for the 6" vise. Here are a few stats that may help with your decision. According to Glacern's website, the distance from the clamping ears to the back of the vise is the same for both the 5" and 6" versions. Therefore, you shouldn't gain or lose any more travel toward the column with the smaller 5" vise. However, you will loose a significant amount of capacity with the 5" vs the 6" vise. The 5", per their specs, only has a jaw opening capacity of 5" vs 8.95" on the 6" vise. If their specs are correct, that's a significant difference. I am not sure if the vise jaws and accessories are the same for a Glacern as they are for a Kurt, but if so, there will be a world more of new and used accessories available for the 6" vise vs the 5". I have a 6" Kurt and have used the 8"+ of jaw opening capacity on numerous occasions.