Due to an issue with MT4 Builds 940 and 950, you will be required to do the following steps each time you wish to set the spread (thanks to Radu.hu for this solution):
1. Launch MT4 as usual via the Tickstory launcher.
2. In the MT4 Strategy Tester, select your desired spread.
3. Select the “Control points” modelling type and press the ‘Test’ button. You can immediately stop the back-test once it has started. The selected spread will now take effect.
4. Select the “Tick” modelling method and continue back-testing as normal.
5. Repeat steps 2-4 whenever you wish to change the spread.