For your Condensation Cure Silicone Rubber, i was wondering if theres any reason why I wouldnt be able to mix in Fillite poweder to bulk up the main body of  my mould and stiffen its outer walls with?

Looking at this guide https://davidneat.wordpress.com/tag/adding-fillite-to-silicone/ it suggests you can use fillite to bulk up silicone at the cost of stiffness... The reason im considering this is because my mould im looking to make is actually a little larger than i expected and im not sure I have enough silicone to make it now. However ive ran out of money and need to try and extend the mould. 

I'm thinking I can mix up my silicone batch, pour say half the batch on my design and let that get all the details. then quickly mix in the fillte into the remainder and poor that on top of the unmixed silicone.

The stiffness would actually be helpful as I cant make a big mould the stiffness would help with keeping the mould shape true.

Ive ordered some fillite (its really cheap) but i just wanted to be certain with you guys that it shouldnt cause any real trouble? like inhibiting the cure or not "bonding?" even though it seemed to in that guide. 

Any help would be appreciated. 
Thanks
Stay safe.
Simon