This spring I realized that I've not been able to keep the seat in place and I don't dare wind the seat clamp any tighter. It invariably slides back slowly until stopping at the rail bend, takes a few weeks but sure enough, it moves back. Is it permissible to take a file and slightly roughen/groove the rails to give the clamp something to grab? The saddle is a Spec Toupe +

I had a similar situation with my Motobecane 700HT MTB. The saddle kept slipping downward. I started looking at the clamp and found it was not tightening against the rails because the bolts were not threaded properly. I contacted the dealer and got a new seat post. This fixed the problem. Check the clamp closure on the rails and the bolts.

The saddle slipping is due to the clamp being not tight enough.

Why don't you want to tighten it further? It's not that your saddle has carbon rails that makes it scary to overtighten. Your saddle has CrMo or Ti rails.

If it still slips after proper tightening, you can wrap your rails with anti-slip tape, like the ones they use on slippery surfaces for traction.
3M™ Safety-Walk™ Slip-Resistant General Purpose Tapes

I'd suspect the clamp's not tight enough or there's something contaminating the clamp or rail surfaces, acting as a lubricant. But if the surfaces are clean the the clamp's tight and you still have slippage, maybe carbon assembly paste or even Loc-Tite could help prevent the rails from sliding in the clamp.

try texturizing the actual saddle rails .... vibrating engraver was my tool.

I'd remove the seat and tighten the clamp to see if it's bottoming out early.

If not, your idea of 'too tight' is a bit light-on, I suspect.

Thanks. I've done a bit of internets searching and it's not an uncommon problem. Solutions include:

Abrasive paste
Light sanding of rails with coarse sand paper
Etching of rails
Torque to a spec (I've no spec, the bolt seem a little small).
Grease
Loctite
Disassembly of the clamp & inspect
Grease the tightening bolt(s)
Electrician's tape
Inner tube wrap

General consensus; is it's not tight enough but that something else is going on. The rails are super slick & appear to be stainless steel. I noticed the clamp surface appears smooth as well. I suppose there's a silver lining here as I discovered in fiddling around with it that it's also the source of the creaking that's been driving me crazy.

Update; while on a cross state biz trip in the Tricities I spent an evening and dismantled the seat clamp. There was noticeable grit on the clamping surfaces so I cleaned them and the rails, the bolt screw threads, the "nut" surfaces (the nut is a cylinder that can pivot) and the surface the nut pivots against. Then slightly lubed the bolt screw threads and reassembled. I immediately noticed the clamp cinched down smoothly and without any grinding or crunching sounds, creaks or groans and I stopped several times and grabbed the horn and saddle seat and physically worked them to see if I could work any play out and I couldn't. Without a torque wrench I was guessing on the torque but I suppose 50-60 inch pounds? Maybe slightly more? The upshot? Saddle no longer creaks or moves and I assume the grit was acting like little ball bearings between the hard stainless steel rails and hard anodized seat clamp metal (aluminum?). Funny, the seat clamp appears to be an alloy but I can't believe its aluminum because the clamp horns are pretty small. Thanks for all the advice.

i agree