My DIY Lsi15 stand, need idea for cone?

Hello,

I just purchased some used Lsi15s and they didn't come with the spike stand:(

I've built a temporary stand with some wood, lag bolts for spikes and some washers and spray paint (see pic). Does anybody see any potential drawbacks on my stands?

Also, I need some ideas for the cone that points inside the port hole underneath. Does it have to be made out of medal like the LsiC?

I was thinking of making one out of dense foam coated with cement or plaster because my friend has a foam molding business and he can cut any shape out of foam. Free of charge, any drawbacks?

Thanks for your time