Problem in Signa

[motormount]

Hi...

I'm trying to impose 3 different booklets on one imposition.

They should be printing together, first plate signature 1 of each booklet 
2nd plate signature 2 of each booklet etc.

I'm preparing the first imposition choosing the plate and scheme i want, then i make a new product part not choosing a plate but only a scheme, and then when i drag drop the new product part scheme into the first product part plate, only the signature i drag'n drop gets to the plate...

Do i have to drag n drop EACH signa manually into place??????

I remember i had done something similar a couple of years ago, and somehow all the signa's of the second product part got into place accordingly  as soon as i placed the first one....

I' trying half an hour now and not getting anywhere....

Signa 11 here!

Thanks in advance!