The 4000 series may be adjustable, that does not apply to the rivets. Those supplied are fine for most of the positions, but where there is a large buildup of glass and Araldite such as at the bottom of the footwell and fuselage joins, they are definitely too short. Grinding down the area helps in some cases, but you can't do that too far, so for the difficult ones I resort to the Europe supplied rivets. If you are considering this solution, it may be worth getting Milspec to send you 10 or so longer Cherries.
Tip: If you mispull the Cherry rivets they are impossible to drill out. The only way is to use a powerfile to sand off the other side, then use a punch to knock it out.