Advice needed Shorting UK Long Guilt for Long Term!

Over the next few months I wish to open a short position in UK Long guilt thought Finspreads. I am prepared to roll this position over with up to a five year time frame as I'm in no hurry and believe UK Government borrowing costs will rise at some point.

I need help choosing an ultra safe stop level that will never be triggered and advice on whether financing/rollover charges would be excessive and make the trade impractical.

Stop Loss

I'm looking for a stop loss level that will never be triggered. If I was long FTSE100 my stop would be 0; Long GPD/USD would be 50 cents; Long Gold would be $200.

The current quote for the UK Long Guilt 10y is 117.12. I believe this equates to a nominal yields of around 2%. I thought a stop level of -3% or -4% would be safe, I don't know what that equates to in price.

Financing/Rollover

Can anyone who trades these regularly tell if the financing/rollover cost of this position would be expensive or cheap. The stop loss would be lowered when rollover loss was incurred.

Shorting the German Bund is another option

Thanks for your help and understanding. Your expertise is appreciated.

- Steve