A hack that modifies the values for UIFont read-only properties ascender and descender.

UIFont+Manipulation.swift

// A hack that modifies the values for UIFont read-only properties ascender and descender.
// Usage: UIFont.manipulateFont()

extension UIFont {
    
    static func manipulateFont() {
        swizzleFont()
    }

    static func swizzleFont() {
        method_exchangeImplementations(
                class_getInstanceMethod(self, #selector(getter: descender))!,
                class_getInstanceMethod(self, #selector(getter: swizzledDescender))!
        )
        
        method_exchangeImplementations(
                class_getInstanceMethod(self, #selector(getter: ascender))!,
                class_getInstanceMethod(self, #selector(getter: swizzledAscender))!
        )
    }

    private var isHelvetica: Bool { // modify this property for your font
        fontName.contains("Helvetica")
    }

    @objc private var swizzledDescender: CGFloat {
        if isHelvetica {
            return self.swizzledDescender * 1.05
        } else {
            return self.swizzledDescender
        }
    }
    
    @objc private var swizzledAscender: CGFloat {
        if isHelvetica {
            return self.swizzledAscender * 0.95
        } else {
            return self.swizzledAscender
        }
    }

}