My requirements were manifold: the new piggy back should support:

I started with a base platform as close to the centre of my TAL-2M mount as possible, thus ensuring that the balance of my scope was not disturbed.
I used a piece of hard plastic (Trespa), 2 PVC brackets with long bolts and 2 pieces of wood.
On this base plate I can screw my Witty slow motion controller

The sturdy bolt in the middle is used to fasten - with a wing nut - the fork mounting of my Maksutov 100/1000 Scope and the aluminium strips allow the fork to be adjusted in azimuth.

Apart from the above mentioned Maksutov I want to be able to use my full range of SLR Photolenses to ride the piggy back platform and I want to be able to use my webcams and also my (rather heavy) Nikon Coolpix 995.

Therefore I have made 2 top level platforms to mount on top of this piggy back base platform: a heavy duty (mainly for my 300mm SLR Photolens and also a lighter version.

Home made piggy-back mounting - heavy duty platform

Here are some pictures showing the construction: below each popped-up image you will find explanatory text.
On July 14, 2005 I started to use this piggyback platform with 400mm SLR Photolens and 2x Teleconvertor for Autoguiding !

Home made piggy-back mounting - light platform

Here are some pictures showing the construction: below each popped-up image you will find explanatory text.