I need to look at a few things about stability at high speed.
Fact or Myth - small wheels have less gyroscopic effect and are therefore less stable?
Issues to look at, a small wheel turns more quickly, so if the mass is about the same is the effect the same?
http://www.gyroscopes.org/math.asp
Does the force amount to much anyway?
Extending the fork link should create more trail, will this help that much with high speed stability.
Without Rider:
Front 40 Kg
Back 68 Kg
With Rider:
Front 65Kg
Back 130Kg (Note: Cannot go above this for speed rating of tyres)
Conclusion: I can add up to 70Kg of lead to front if need be
Solution: Lead tyre weights from the local service centre. This is 30Kg and will reduce in size if the weights are stacked.