EDP question: unrounded multiply directly into overdub?

[Rainer Thelonius Balthasar Straschill <moinsound@googlemail.com>]

Hi EDP specialists,

I have a EDP-related question:
First of all, I don't have an EDP available, rather am writing something 
for an EDP user, so the "try it" version does not work here...

So, here's the use case:

I start to record a loop with 2 beats length, then switch to half-speed 
- 4 beats. Only other modifications are overdubs.
Then (while still in halfspeed), I want to shorten the loop to its first 
half (2 beats) and immediately go into overdub.

I seem to understand that for shortening a loop, the only way is to do 
Multiply->Record. So how do I get this immediate overdub after I end 
multiply? Tricky Quant/Round settings?

            Rainer