first thing you could try is trimming the motor to get the bow down at low speeds. the foils do help with stability while cruising at speed and can help with performance but they are not suited to all boats

IMO they should be the last resort after everything else has failed. In a lot of cases they have made the boat worse than before they were fitted.

Have a look at where your weight is, could be everything is down towards the stern. Try moving some forward as you are travelling slow and see if it improves.

Maybe even repropping.

I had a foil on my old tinny and it made following seas horrid.

yep last option first look at weight distribution find the lcg logatudial centre of gravity. Look at moving fuel forward even batteries engine set up is critical engine height prop selection go to your dealer pay a deposit try different props 3,4,5, blade different pitch,diamater look at rake and cup .Props are all built for different jobs some push load ,bow lift, stern lift, topend  a well setup rig should not need a hydrofoil to stop bow lift and get on the plane their is a lot of trial and era but it is worth it cause the rig will handle better have better fuel econom yand you will have a lot of satisfaction for achieving your desired goal.i might be getting away from the question at hand but i have allways had 2 different pros for my boats one to push load on the big boys fishing trip then one for hull lift and topend for the quick spearing trip when you run lighter loads and conditions are glass.i have fitted many four stroke engines to early Haines Hunters which were not built for heavy four strokes and not one had a hydro it was all weight placement and setup.

my personel experience with a hydrofoil was bloody dangerous almost tipped my old swiftcraft a few times out of no where it would bite in and drag the boat down on one side and almost throw you out never did it again once i ripped the bastard off . I would recomend you look at putting a set of wedges on if you are having trouble trimming the boat as well as the above mentioned weight distribution

my personel experience with a hydrofoil was bloody dangerous almost tipped my old swiftcraft a few times out of no where it would bite in and drag the boat down on one side and almost throw you out never did it again once i ripped the bastard off . I would recomend you look at putting a set of wedges on if you are having trouble trimming the boat as well as the above mentioned weight distribution

i have a 6.1mt centre cab alli x 150 4st, all of my previous boats i had installed the older black wing type foil as i could not install trim tabs , the foil did improve the ride in most cases ,as without the foil the boat took a long time and revs to get up and planning, on my present rig i have a  different type foil, grey unit with curved edges , The black unit  did bite in when turning and didnt let go until you backed off on your speed.  My present rig i have moved the fuel tank forward and moved all gear forward as possible but still had the issue of dragging the rear end at low revs, i have been able to install QL tabs for trim but have found the new foil in most cases helps, being centre cab i still have to move gear around depending on the seas, i have changed props and did sea trials to evaluate for fuel economy and WOT speed, and ride and actually found that the foil does help and improve the ride with the better prop in most cases,   this is also depends on who the skipper is and how he wants the rig to ride,  if they dont work you can always take it off