A few very clever individuals where I am have got a "top plate" arrangement for their starter boxes. Here's what you do.
1) On your starter box set the pins where you want (doens't matter where) and it helps at this stage to take the top "lid" of your box comepltey off your starte box which will make the following tasks a lot easier.
2) Get a piece of ply wood, or perspex, and drill holes that match the pins you positioned in task 1. Note that a thinner material is more ideal, as it will be less of a hinderance when you get to task 7. The material doesn't really need to be strong, because all this piece of wood/plastic will do is sit on the top of your box. It's not going to hold up your car or anything.
3) Now you will have a sheet of ply wood sitting perfectly on your starter box lid.
4) Cut the hole out of the piece of wood to allow the rubber wheel to push through the ply wood.
5) place your starter box lid (with the piece of ply wood on it) back onto your starter box and line up your buggy on the piece of ply wood, making sure it lines up with the rubber starter wheel.
6) insert pins in your ply wood (generally a piece of dowel is good for this) to seat your buggy nicely on the piece of ply wood.
7) fix your starter box lid back onto starter box, and check that the rubber wheel doesn't get obstructed by the box itself when you push the lid down. You may need to cut a bit more out of the actual starter box lid, because the rubber wheel may not reach high enough to touch your cars fly wheel with the piece of ply wood in between.
Now to fit your truggy, basically make another piece of ply wood, and at task number 5, mark your pins out for your truggy. So now you will have one piece of ply wood for your buggy, and one for you truggy. You jsut swap that top piece of ply wood depending on what car you are starting.
Again, this idea is what some folks at my local club use... i saw it and thought it was a great idea !!!
You could try that out if you're up for it.
Cheers