Was about to get a toy- then I did some research...

[AndyUK]

2. This might be impossible to answer without more details, but I'll give it a go. I currently have planned about 150mm of Z travel which would make the gantry plates roughly 500mm in height as measured from the X (long) axis side mounted rails to the top (ie the plates would extend a further 100mm below the cutting bed). Does this seem OK or would it be advisable to give up some Z travel in favour of shorter gantry plates?

You'll always get a stiffer solution with less Z travel, but I wouldn't have said 15cm is unreasonable. Also depends on if the bed is adjustable or not - if not you have to consider the clearance height of any clamps or vises you plan to use. Having said that, it sounds like you're implying a 25cm (500-100-150) tall gantry? Without seeing the design its hard to say, but sounds quite hefty!

[Juranovich]

Sorry, I might have been a bit unclear in my description, essentially the gantry plates would be roughly 60 cm in total height. But what matters, I suppose, is that the gantry would be 18cm + two round linear rails mounted top and bottom adding a further 5cm or so to the overall height of the gantry. While the space between the non-adjustable bed and the bottom of the gantry (including the rail) is 20 cm, the free height from the tip of a typical router bit on a mounted spindle down to the bed is 15cm (when Z is in its top position). Hopefully that cleared thing up a bit!