Southern Cross

I have been building the ultimate touring car with my Tamiya TRF416. Seems like its taking forever...waiting on all the little bits to come in from Japan...Canada...Hong Kong...now I'm just waiting on my ESC cooling kit...anyway. My Tamiya Foam inserts finally came in today. I'm torn between using them or the standard foam that came with my tires. They are both Tamiya medium-narrow. I'm a little concerned about the foam inserts I got for it...they are the ones you see pictured in the manual. Here they are along with the tires and foam I'm talking about.

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The "standard" foam I am talking about is the stuff you see in the pic of the radials above..t.same tires I am going to use. I installed the foam inserts on my rims and the fit, while okay, seems like it is not nearly as good as the standard foam. They hug in the right places...it just seems like they don't fill the tire out enough. Its like there's a mm or two between the foam and the tire. Seems like it was cause some problems at speed...or at least do their best to slip...even when glued. I was just wondering if anyone who has used the Tamiya foam inserts pictured above in their tourer...and what you thought about them compared to standard foam. This rig is going to be raced indoor and out...as wellas a good bit of high speed asphalt action.