This from WFTF website.
2.4 Reduced diameter hit zones. The total number of targets with reduced diameter hit zones may not exceed 25% of the total targets on that particular course. Maximum distance limitations for such targets are as follows:
So according to the rules ( or no rules as the case may be) it's 25%, but a quick phone call to El Presidente can up this to 40%.
Can of worms....
The Pope HW97 V-Mach. Gary Cane Laminate stock. Leupold Competition 40 mag Mildot.
The Smiler. Walther LGU. WE Laminate stock. Leupold Competition.
The Dark Destroyer. TX200 MK3. Leupold Competition 40 mag.
Pro-Sport. Warren Edwards Blue Laminate stock. Bushy 8-32x40.