Bent exhaust

Hi guys

I has a minor crash earlier last month which resulted in some damage. Most of it sorted now, except the exhaust. I have a (formerly beautiful) Arrow full system on it. The can is scuffed, I plan to replace that just for cosmetic reasons, still works. However the titanium pipe itself (the downpipe?) which runs under the engine from the front cylinder is bent as it hit the kerb (which brought the sliding bike to a stop). The shop who repaired the brake stuff said it's rideable with the dent but I estimate from looking at it that about 1/3 of the diameter is lost. Most importantly it looks rubbish! I emailed Arrow to see if they can send out replacement sections (the whole lot would cost just shy of £600!!). But no reply (posted 2 weeks ago). So - does anyone know any cheap fixes for dented/bent pipes? I've searched all over the net - I noticed motocrossers use the trick of freezing water in their dented header pipes overnight (expanding ice pushes dent out). I'm considering trying this, if can find something suitable to seal each end. Or any other ideas?

Also, could the slight loss in diameter damage the engine, or just result in a barely noticeable loss in performance?