Your hardware inventory changes by the day!
You can't stack 4500X's so the horizontal link should be confgured as a VSL to make them a VSS pair. This will allow for the ASR to 4500X links to be configured as MEC links.
I have redarwn it is a logical diagram (attached) as it cuts down on the lines, but for each aggregation point (4500x and 3750X) just know that all of the Po links are split between the chassis.
The only caveat of my diagram is that the links to the ISP routers have no physcial redundancy like the rest of your network, but I guess you will design-in outbound routing redundancy on the 4500X via PBR.
Don't forget to rate helpful posts!
cheers,
Seb.
