Inspect closely to see if, after years of use, original Ali & even Stainless pop-rivets are becoming slack or quite loose.
E.g. At the flat sheet wrapped round the 'tailcone'.
Also those diagonal fuselage cross bracings inside near the control column base. The firewall rivets joints can weaken by the bottom corners too - on U.K. builds it comprises thin Stainless Steel over an Ali sheet & they are lightly pop-rivetted on. The Rans build book shows how & specifies the correct components.
Otherwise considering its very light construction this microlight has withstood the years exceedingly well.
An engineer's tip for drilling out rivets...."Just drill the head slightly, then knock it with punch, this should shear the head off, reducing the chance of making the hole larger."
For the S4 tail 3/16 SS pop rivets came overnight from Rans U.K. Agent 'SkyCraft', two slack ones were drilled carefully to remove, as advised and the new ones set.
The firewall itself can suffer small cracks too. A doubler plate can be rivetted on. See two pictures of left side stainless crack before and right hand side - during a repair. [Two rivets not yet set].
Those rivets can be the end-all or be-all of the aircraft hardware so the trick there is in the drilling but more often than not, the firewall helps to protect it from any possible crack.
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