got some linear slidey doofers

want a little plasma table

first question, the linear sliders are solid round
the lengths are 700-800mm
is that ok for a tiddly plasma table?
i have another one as the loose one in the pic
the plan is to widen the lower twin rails parts
to utilise the length of the y axis
then chop down the other one for a z
what length do i chop it too, do i need more than 50mm travel for a plasma?

any one near west london fancy doing some machining