If your talking about the R kev made a set of rear raiser links, not 100% sure what the size of the link is but it raised the seat about 2inchs/5cm, but also rasied the end etc a little giving more ground clearance for off roading.

The front end is no problem just puts more pressure/wieght on the front tyre, so your front tyre will wear a bit quicker, you will feel it being easier to switch/turn quicker.

The only real down side is the chain start to run on the underside chain guide roller (those wee rubber rollers to stop the chain from slapping/moving about) it rolls on it all the time and can wear it out alot quicker.

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Plough on