Freestyle scooter info for parents and kids
It looks like they are standard diameter bars, so you could get them to work with IHC by cutting a slit in the bars and using a standard diameter clamp.
Yes, you'll need to cut a slit in the bars. Threaded forks and threadless systems require a slit in standard diameter bars and a standard diameter clamp.
The Madd Gear VX5 has an IHC fork, so you'd need to replace the fork with a standard threadless (non-IHC) fork.
I answered this on your comment, but here's the answer for everyone else as well:
It's almost certainly a 5mm hex bolt, so you need a 5mm allen key. Finding one long enough for IHC might be tough. If you can't fine one locally, Inward Scooters sells them for $5 - District Extra Long Arm ICS Allen Wrench Metric # 5. Unfortuantely, it looks like they are sold out right now. Give them a call and see if they can help you out.
You could technically make them fit by stacking an HIC shim on top of the IHC shim, but you should NOT do that as it will be very unstable.
ICS is for standard diameter bars and ICS-compatible forks only. Also, the MGP Hothead fork says it requires oversized bars for HIC: http://www.thevaultproscooters.com/shop/madd-gear-mgp-hot-head-alloy-thr...