[Groff] tables side-by-side

[James K. Lowden]

I'm confused about how best to lay out tables side by side.  I'm using
the ms macro set.  The main text stretches across the page (one
column), but I want the tables adjacent so that they can be
more easily compared.  

My basic approach is

.mk
.TS
 ... table 1 ...
.TE
.rt
.DS 3i
.TS
 ... table 2 ...
.TE

If the table is too long for the current page, and lands on the next
one, that doesn't work well at all, so I have

.KS
.mk
.TS
 ... table 1 ...
.TE
.KE
.rt
.DS 3i
.TS
 ... table 2 ...
.TE

In both cases, though, the second table isn't quite lined up with the
fisrt.  I use .sp to move it down, sometimes by 5p, sometimes by 5
lines, depending on whether or not a keep was needed.  

I'm obviously doing something wrong, because 1) the second table doesn'
line up, and 2) the way it doesn't line up varies, and 3) the keep
behavior varies according to where the table falls.  

What's the right way, please?  

--jkl