1. How do I position the core centrally in the mould - I'm assuming some sort of jig will be required to hold it in the right place but if anyone knows of any online tutorials or can describe well how to make something like this - that would be really helpful

2. how do I ensure lack of voids in the mould - I'm presuming injection moulding would help with this but am unsure of the practical details of how you actually go about doing this! So far my experience is limited to 2 part mix and pour stuff.

3.how do I ensure even foam density throughout the weapon (so I don't get patchy hard bits) - I'm thinking this might be easily solved just by good mixing but any tips appreciated

many thanks in advance