Don't need this anymore. I ended up using two sets of anti fatigue mats from harbor freight ($6.99 ea before coupons), which enabled me to trip each 1/2" level so it fit the topography of the bottom and sides. I also ended cutting my old foam insert to hold the jack, and moved that to the passenger side of the spare. I bought a foam spare insert for a G37 on eBay for $35, and it is good to go. Not perfect, but for less than $50 total, I don't think you can beat it.
Ideally you would want the mat for the back the fits the spare as the non spare mat has a 4" lip on the inside edge. I spaced/supported that out with the foam edge pieces and can still access my pass through.
I ended up cutting the spare insert to fit my manual so I opened up some glove box space as well.
All told, I lost about 4" of depth, but for piece of mind to have a good spare and no RFTs anymore, it was worth it.
See the pics below for details.

 

Q50 Trunk foam insert

I'm looking for a trunk foam insert for a Q50 without a spare.

Would appreciate any suggestions.

CB

 

do you mean you want one for a Q50 without a spare? or you are looking for the foam to convert one without a spare to a spare?

If you are looking for the foam for the non-spare q50, there is a steal on ebay right now:
Ebay foam

 

Nice alternative to the foam inserts, is it possible you can elaborate a little more on the how you measured the space to cut the shape of the mats and what tool(s) you used to do so? Thanks.

 

Sure no problem.
When you buy the anti-fatigue mats there is a paper sheet in the packaging. I took that sheet and cut it to give myself template of a rough fit of the space I needed to fill, and worked it so I could get two layers out of a single thickness of mat(see the pic). Since the mat is 1/2" thick, I could get 1" per piece and therefore 4 inches per side (took me two packages). I then went and fit it to the space, and put the paper back down and built each level as I went, so it contoured to the space. I then held everything together with rubber bands.

I cut everything with the $0.99 harbor freight snap blade utility knife on a large cutting board.

Hope that helps.

 

Thank you for the write up!

 

The foam inserts are going to be very inexpensive if you buy from a salvage yard. Not to take away from the OP's ingenuity, but I think in this case the time and effort isn't worth it, since I bet you could get a salvage yard to shape the inserts to you for less than $50.

Refer to this thread.
https://www.infinitiq50.org/forum/showthread.php?t=106018

 

Damon, just as a heads up, i did call,and was watching on eBay...the best price i could get from a local salvage yard was $150 for the set (and shipping because of size was very high even though the weight was low), eBay it is $50-60 per piece! (They must be able to look up what these parts cost new and are trying to squeeze ya!)

I think my $14 solution is not a bad way to go (if you have a harbor freight nearby that is).