The unit would not get "hit" by the Residual FP (Fire Lane or normal) on the 2 MF spent...both MF are expended before the Residual FP is placed.
I do not see that this is true. A MG retaining ROF or a unit using Subsequent First Fire may fire at a unit a second time on the 2nd MF (or greater) spent to enter a building/wood/etc., the only restriction of RFP attacks based upon a MF expenditure is
A8.22 "
• MF/MP expended "simultaneously" (e.g., two MF to enter a building, two MF to cross a wall and enter Open Ground, eight MP for a truck to ascend a Crest Line, etc.) do not cause multiple Residual FP attacks." If one were to fire at the unit entering the terrain costing multiple MF to enter and had fired on it on the 1st MF expended (as most people do in order to possibly retain ROF or use S1F
[A8.2 When a unit is attacked by Defensive First Fire/Subsequent First Fire/FPF, the target Location in which the attack is resolved (even if in Bypass) is marked with a Residual FP counter...]), RFP is placed then. Since RFP has not attacked the moving unit previously it would attack the unit on its 2nd MF spent
but be unable to attack it again on any additional MF spent to enter the hex as explained by
A8.22. No where do I see that RFP is placed upon the completion of a move, simply that it is placed upon the completion of the initial fire (i.e. the shot at the 1st MF spent). It does say that RFP does not attack until a
specific activity such as Searching/ Recovery/Placing Smoke Grenades/etc. has been completed, but does not imply that entering terrain at an increased cost falls within that purview. Granted I have rarely seen it enacted as I propose, but the rules simply do not seem to bear out the contention that it is RFP is placed after all initial MF to enter a Location are expended. Furthermore, if that were he case, a S1F shot (or ROF shot) at the unit based upon the expenditure of of a 2nd or subsequent MF expenditure to enter the Location would also be denied and this is simply not the case as I have seen.
EX of Play: A squad and MG fire at an enemy infantry unit entering woods declared at the 1st MF spent (assume no cowering and ROF for the MG); by rights (A8.2) the RFP should be placed immediately upon the resolution of that shot (A8.2); now the unit opts to fire S1F or a 2nd shot with his ROF MG at the 2nd MF spent to enter the Location, but first if one follows the criteria of A8.2 the RFP would attack first.