Dividing numbers by constants without dividers?

You can use lpm_mult if you want, it gives you direct control over the primitive, but if it makes the code easier to read why not just stick a multiply directly in the code and let the synthesisor put the multiplier in? As long as you register the inputs and outputs it should infer the registers inside the DSP slot.

If you have trouble with timing, the problem is more likely the routing in and out of the DSP. If this is the case, just add extra registers in the pipeline in your code. But At 178MHz, I dont think you'll need them.