It's not the size of the joists or posts its the span and load.

JonMon

I built my deck with ipe posts/rails/balusters and the weight is not a problem (although man those pests are bulky!! :))

Keep in mind when using ipe lumber. It's wood.

The larger the wood is the more movement.Back when I did install solid 4x4 / 6x6 Ipe rail posts I learned they will have surface checks come up quickley. We delt with them in the shop with tightbond111 / ipe sawdust and the makita random orbit before they went to the site most often they come up one time only.

Now days I put pt custom posts in the frame ,make posts wrapps with 1 x 6 /1 x 4 ipe and slide them over the posts after the decking is on.

Far as the weight puting extra stress on the frame,it would have to be a pretty bad frame job for that to make a differance.

JonMon,
you can see these post wraps on my site
www.deckmas....O wait!!! the garden police wont let me show any of you that I wonder if I will get kicked out for talking up tightbond111??? and promoting that Business. And Dammmmm I said Makita as well!!! Man it's like walking on eggs over here latley. J.