Drilling through Glass fibre reinforced resin seats - risks to be aware of?

[Time Waster]

I've got an old HPV Streetmachine GT that I'm getting fettled ready to get some use out of it after 3 years of storage. It's a solid enough touring recumbent but it's not completely practical. Buy a touring upright you get 3 bottle cage bosses, spare spokes stored on the frame and several bosses for attaching stuff. I'm not sure touring recumbents, certainly not two wheeled ones that I've seen, have that higher level of practicality built into them. My venerable SMGT certainly doesn't.

I've read in a copy of the user's manual I found in an archive site, HPV simply do not want to even acknowledge there was a gt version before the current GTe version, that you can drill holes for attaching bottle cages either side of the seat. There's two sets of locations you can do this, mirrored on both sides. There's the lower seat and behind the shoulders too. This means drilling the holes in those specific places only. It's a GFRP seat.

Does anyone know anything dog this weakening the seat? Do you have to only drill those seat locations? Is it only allowed for hole location or can you use both locations To get
bottle cages?

 

[recumbentpanda]

If I remember rightly my Nazca Fuego seat has sixteen holes for mounting brackets, rear rack and headrest. As grip is a mesh or web, small holes have little effect on overall strength unless too close to an edge. Main issue is the drill skating on the gel coat as you start. Put masking tape on mark out holes, and use a sharp object to start.

 

[slowmotion]

Use a new high speed steel or tungsten carbide-tipped drill bit. If it's blunt, it'll overheat the gel coat and make a mess of it.

 

[Tigerbiten]

I ended up using a brad point drill bit to drill drainage holes on my hard shell seat.
I found this type of bit better than a HSS bit.
It's less likely to wander at the start and it can give a cleaner hole.
Unless you crash badly, I cannot see how a few holes drilled will weaken a seat to everyday use.

Luck .......

 

[Time Waster]

What weight rating do these seats have BTW? The SMGT one looks very over engineered. I guess the warning to only drill in those 4 points is a risk adverse company protecting itself.