I don't know how the Foma paper will respond to it (Thomas would know) but to get slightly deeper blacks on neutral toned papers you can try selenium toning. For this you usually use more dilute toner than you would for a more radical color change. Many neutral tone papers will cool slightly with a slight increase in d-max and contrast. I use Kodak selenium toner at 1+19 for somewhere around 5 minutes. With the Adox MCC 110 paper I've been using I stop at 4 minutes because 5 starts giving me too much purple eggplant color I don't really care for.