I just replaced the decking on our covered entrance porch with T&G ipe
decking.

Now I need to find a way to re-anchor the porch columns and railing
posts back to the decking or joists below. The posts which I am
re-using were previously just toenailed to the decking (and maybe the
joists below) with 16d or 20d galvinized finish nails.

If the new deck were regular wood, I could have either toenailed in
finish nails again or toenailed in trimhead deck screws.

The challenge with Ipe is that it needs predrilling to prevent
splitting or breaking of the fastener.

However, for toenailing a post, I would need a drill bit that is about
4 inches long in order to go through the post and then into the
decking and beyond. But, they don't seem to make thin drill bits in
that length (or at least I couldn't find them in the Big Box store).

The only alternative I can think of is to use something like a 1/4"
lag bolt but that would require some serious countersinking of the
head and seems a bit of overkill.

So any other ideas on how to fasten suports to the deck surface (note
since I am using the existing design with the existing posts and since
I have already applied the deck, I don't have the luxury to redesign
the post system)